Konstantin Zhuravlyov is missing for two weeks after crossing from Turkey into Syria.
Only way to save the Middle East country from 'endless bloodshed'.
Viktor Gorelov, 66, was kidnapped by armed Syrian rebels on 12 December during a work trip to the strife-torn country.
FSB say Konstantin Zhuravlyov, 35, is now back with his family in Tomsk after being held as a 'spy' by Syrian opposition.
Officials probe report of militant trying to recruit young Russians to the cause in Syria at city university over 18 month period.
Criminal cases launched against pair recruited to Syrian terror groups affiliated to Islamic State.
Oleg Peshkov was killed when the Turkish air force downed his Su-24 over Syria as he battled terrorists.
'I've got to talk to my British colleague,' said the Russian president as he left a key fuel and energy session to take the phone call.
Anatoly Zemlyanka, 28, came from 'normal' family in Noyabrsk, and was into Thai boxing and karate.