Not really. Simply because if a key was a REQUIREMENT to get OUT of the cottage, we would certainly have heard that testified in the trial...it is hardly a mere 'minor detail'.
By your logic, surely we would also have heard if you DIDN'T need a key to get out of the cottage, since that would be an equally important detail? Your evidence here is basically...lack of evidence. That's pretty weak.
And besides, Micheli at least did believe it possible that Guede could have been 'locked in'. Any ideas as to how that could've been possible without a key?
I would also add, IF there is a requirement to use keys to get out of the cottage (even if there isn't in fact) the keys would have been unlikely to have been in her purse or pocket, put rather put down on a side or table somewhere (ditto the phones). That's actually what most people do with their keys. They don't want to be having to rummage through their purse for them every time they have to take out the rubbish, answer the door or pop out for 5 minutes.
Actually, they were most likely in her purse. We know this because Guede said she put them back in her purse after she came into the house; in his version, of course, he was there with her when she did so, and this is how he knows where they were.
The alternative, of course, is that he was the one to take them OUT of her purse. Isn't the fact of her keys being in her purse a slightly odd detail for him to just make up, unless he was trying to add credibility to his 'date' story by embellishing it with details he knew to be true? And how did he know this particular detail was true, unless he took the keys out of her purse himself?
For that matter, how did he know her money was missing? He claimed that it was missing before the attack happened, and that Meredith blamed Amanda. Doesn't that sound rather like the kind of story you'd make up if you knew that money had been taken, and were trying to create a plausible cover story to make sure you weren't blamed for it?