screw missing from scope base

I am in the processing of cleaning (boy is this thing filthy) a varmint rifle (bolt action Remington XR-100) in .204 Ruger for my nephew.

When I took the scope off of the gun I discovered that one of the screws in the Leupold scope base was missing (has 1 screw at rear of base and 2 holes at front of base & gun receiver and 1 of the front screws was missing).

Is it possible that he could be losing some pressure/gas out of this open hole in the top of the gun receiver and scope base ? I know that this hole is behind and above the gun's bolt face and bullet chamber but even so could this be problematic ?

Should I search for a screw to use to insert/fill in the scope's base hole and gun's receiver or will having just the rear screw and the one (1) front screw be sufficient ?

Thanks.

Is the hole in question threaded or not ????? A close-up photo of the area you are concerned about would be helpful.