Its definitely retrievable - I know from personal experience having done the same thing.
If you are a bit brave with pulling back the carpet you can just about get behind it enough to fish it out from the bottom of the footwell - it requires the carpet to be pulled away from the door area a fair bit but it will push back quite easily and is time wise the most effective method I guess.
I doubt this is the text book solution to the problem but I retrieved it with 3 or 4 minutes and there's no sign of having moved anything.
Truthfully it a pretty daft thing to have a hole in the moulding where the SIM goes, its obvious it will drop down there at some point.
J
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