I would consider them compromised. Before you do anything else, carefully remove the screws and check the raised front bosses on the plastic plate. If you caught it early they may still be ok, but if they are deformed I wouldn’t use the plate. If nothing else it’s good information.
For your Holosun 507C, you are going to need to use 6-32 x 1/2” flat head screws with a small diameter head. I order mine from McMaster-Carr (McMaster.com). They aren’t crazy expensive but if you’re only ordering one box you might pay more in shipping than for the screws.
If you’d rather not pay for a bunch, PM me mailing info and I’ll mail you a couple sets… I’ve got a bunch and since I retired my mounting workload has diminished significantly.
Like I mentioned earlier - once you go to re-mount the optic with whatever plate you use it’s really important to use the correct procedure to minimize the chances of the optic coming loose.