His mother, Andrea Leclair, previously described her son as a "world traveller" and "adventurer".
"I thought I would be there forever," Mr Baxter said during an emotional appearance at a news conference in Beirut on Friday.
Lebanon's security chief Abbas Ibrahim, who appeared alongside him, said he was detained for "reasons related to breaking Syrian law".
Canada has advised citizens against travelling to Syria since civil war broke out in 2011.
"Syria is not safe for personal travel," the advisory on their website says. "Attempting any form of travel in this very hazardous security environment would place you at grave risk."