Freed American Paul Whelan is wearing Biden’s flag pin every day, his lawyer says

Paul Whelan is "looking forward to rebuilding his life" and will return to his home state of Michigan next week after a 19-day resettlement stay at Brooke Army Medical Center, his attorney, Ryan Fayhee, tells ABC News.

Fayhee, who raised Whelan's case with policymakers in Washington throughout his incarceration in Russia, says his client "is doing as well as can be expected" after more than five years in a Russian penal colony where the former Marine said he was subjected to forced labor.

Designated as a wrongful detainee by the U.S., Whelan was swapped two weeks ago along with Americans Evan Gershkovich and Alsu Kurmasheva, in a multi-country trade that sent eight prisoners back to Russia.

"He's continuing to undergo various medical related tests and treatment as any wrongfully detained American who comes home does, and he's looking forward to beginning to rebuild his life, after five and a half years away. And so he's soon to return to Michigan and looking forward to being reacquainted with friends and family and getting his life in order," Fayhee said of Whelan.

Whelan was arrested in December 2018 and faced trial for espionage. He was convicted and sentenced to 16 years in a penal colony on charges the U.S. said qualified his case as a wrongful detention.

Brooke Army Medical Center in San Antonio, Texas, is the "largest and most robust military healthcare organization" within the Department of Defense, caring for more than 4,000 military and civilian trauma patients annually, according to the center's website.

It is the sole Level I Trauma Center in the military health care system.

"That initial triage," Fayhee said, "happens really almost immediately."

"When I met Paul on the tarmac in San Antonio at I think around 3:15 a.m. -- by around 6 a.m., he and Evan and Alsu were all beginning this process."

Another striking moment on the tarmac: President Joe Biden handing Paul his American flag lapel pin. "He's been wearing [it] on his collar every day since," Fayhee said.

Fayhee said Whelan has spent much of his days in San Antonio reading, having brought four bags of books home that were sent to him during his detention. "He's focused on reading all the things about the efforts that his family … and the administration undertook to gain his release, so he can sort of put the pieces back together," he said.

Fayhee reports Whelan having a couple visitors so far as he undergoes mental health treatment. He was even able to take him off base for a steak dinner -- "one of the unforgettable privileges of my life," he said. "It was surreal for me and surreal for him, for different reasons."

The detention of an American abroad sets off a policy process that involves officials at the State Department, which has a dedicated office headed by the Special Presidential Envoy for Hostage Affairs, Roger Carstens, as well as the National Security Council at the White House -- as well as tireless work from family who advocate for their loved one and work with the government.

Carstens told the Washington Post Monday when an American is taken into custody abroad, he treats it as a "forgone conclusion" that his office will secure the detainee's release. Expressing that optimism is an important feature of his strategy to rescue Americans from the most challenging of situations.

Fayhee acknowledged it was "painful for Paul to see others released before him," including Trevor Reed and Brittney Griner, who were detained after Whelan and exchanged in swaps that didn't include his client.

Leaving Whelan out of a deal, Fayhee said, was "part of Russia's scheme in order to sort of re-exploit Paul for the purposes of trying to divide Americans."

"Paul does have some understanding of that," he said.

Whelan's December 2018 arrest "really began, at least as to Russia, this modern era of hostage diplomacy," Fayhee said. "I believe that Paul's arrest really led to the arrest of all the others that came after him …and they really all had to do with the Russians' desire to extract some benefit out of the United States."

Fayhee said the key policy prescription for limiting Americans' exposure to the threat of wrongful detention in Russia is to educate citizens about the acute risk there. He said expediting the process by which the State Department designates prisoners as wrongfully detained -- which would increase internal pressure in the government to prioritize a case -- is an adjustment the government is weighing.

"The State Department -- in discussions around Paul -- has been very open to over the years [to] finding a mechanism to escalate these arrests within the U.S. government to be evaluated for potential wrongful detention," Fayhee said.

"There are key indicators at the time of the arrest that suggest potential wrongful detention and being engaged in those cases immediately, and working them up with the right team within the U.S. government, is just simply critical."

Russian-American Ksenia Karelina was sentenced Thursday to 12 years in a Russian penal colony on charges of treason after her January arrest by Russian authorities while visiting her family in the country. Admiral John Kirby, the White House spokesman for national security affairs, called the sentence "vindictive cruelty" Thursday.

"The sentence just proves all the more that there's no real system of justice coming out of Moscow," he said.

The State Department echoed those remarks but said it hasn't made a determination on whether Karelina was wrongfully detained.

Deputy press secretary Vedant Patel said the department "continue[s] to seek consular access" to make contact with Karelina.

-ABC News' Shannon Kingston and Molly Nagle contributed to this report.