The last question mark is part of the question, not the path name.
I've just run Recuva and it shows quite a few entries with the path as C:\?\Cache\ - something I've never seen, or noticed, before. They are the usual selection of temp internet files. This morning I powered up and ran Recuva and I didn't notice the cache path then. Oh yes, we had a power cut this morning. The temp internet files shown in the cache path are FF files, well the pics are, not necessarily from today. Could this be to do with the power cut?
My FF cache folder in ....\Mozilla\Firefox\Profiles\clgzbh99.default has a create date of today and time of around the power cut. It only has today's stuff in it. In fact I can't access anything using FF offline that was browsed before the power cut. I'm guessing that the power cut made FF throw away its cache.