If the filters look OK otherwise, then there might be some merit in them!
You'd have to find some gaskets, and much depends upon you FCI duration.
For example, if you bought the FL-820s w/o gaskets, and also bought some new ones with gaskets, then each of the "new" could be shared with the "missing"; matched up one for one. Use a "new" filter, then transfer the gasket to a naked one. Repeat.
You could also seek out a gasket in silicone; that would increase the safety odds. Perhaps there is a PureOne filter with the same gasket size, as the MCs are Puro made?
I'd not simply discard the thought of an excellent buy just because
1) some moron stole the gaskets, (possible)
2) some aggravated employee removed them (unlikely)
3) some production run left them off in error (most likely)
At a buck a piece, you could afford to open one up just to satisfy yourself they are OK.
No - wait, I changed my mind.
I'll buy them if you'll ship them to me!