Peralta has failed to return to Glasgow since the end of last season and McCoist admits he has no idea when he is coming back.
The Honduran internationalist is in France with his girlfriend attempting to secure the visa he needs for a work permit.
The 25-year-old was tipped to leave Ibrox last season after newspaper comments attributed to him appeared in his homeland.
He struggled to hold down a regular first team place in League One last season and was quoted as saying he would move on in the summer.
The 30-times capped player was due to represent his country at the World Cup Finals in Brazil.
However, Peralta suffered a thigh injury in Gers final League One match against Dunfermline.
He missed friendlies against Turkey and Israel before being ruled out of his national squad for the tournament in South America.
He has not turned up for pre-season training or the tours of either the Highlands or Canada and the United States.
But McCoist has confirmed he is fully fit after shaking off his knock and expects him to rejoin his team-mates for the 2014/15 campaign. He is, though, just not sure when that will be.
The Gers manager said: "The mystery that is Arnold Peralta is definitely coming back - but when he's coming back, sadly I can't give you a definite on.
"He's been in Paris trying to sort a visa. That's where he is at the moment and we're waiting.
"The good news is that he's fit - the health issues are long gone. It's just location issues.
"We are in dialogue with him, we haven't left him. He just needs to get his visa sorted and that of his girlfriend's. He needs the visa for the work permit. It's not getting it that's the problem - it's the delay that's the issue."
Meanwhile, McCoist has revealed that Cammy Bell, Lee McCulloch and Lee Wallace should both be fit for the Petrofac Training Cup game against Hibs at Ibrox tonight.
The pair picked up knocks in the pre-season friendly match against Derby County at Pride Park on Saturday.
Elsewhere, Seb Faure and Richard Foster, who missed the weekend fixture, could both be available for the first competitive game of this term after resuming training. McCoist said: "The boys came in on Sunday and were iced up, but everyone was training yesterday.
"Wallace is okay, the skipper and Cammy too. We're all out training so that indicates we're in reasonable health.
"Foster is okay as well and Faure has also trained. I'd be hopeful they have a chance."
Tickets for the Hibs game are on general sale and are priced £21 for an adult, £15 for a concession and £5 for a junior. Fans can pay at the Copland Road Stand tonight.