Check Avast’s log file as I asked before and tell us the name and location of the file please.
we need to know that to tell if it really was a infection or a false positive.

Technical corrected me. He is right, there is no move to chest in the bootscan, but you can select move file(s).
If you have used this option, the file should still be in the “moved to folder” unless you have deleted it from there.