If you go to Account Settings >> Tools >> Document Manager, this will list all the files associated with your account and where they’re stored (Receipts being those attached to files).
Does the file appear there?
I assume by this you mean you clicked “Skip” on the Receipt Hub? This should keep the file in the receipt hub itself rather than move it anywhere, so it should still be in the receipt hub.
But even if it was moved when tagged to a purchase, it should appear in the document manager mentioned above.
Did you raise any credit notes in the meantime? I’ve noticed credit notes seem to “block” the next QF number, i.e. my purchases go QF01835, QF01836, CN00199, QF01838, …