Sad situation, because the original bolt was hand fitted to that receiver & numbered to match it.  You may be more likely to find a replacement if you post a notice in the special Model 52 sub-forum at the Rim Fire Central website, but it’s a long shot.

Separately storing any removable part from any firearm for any reason is always a bad idea, & likely to lead to this situation when the owner dies, is disabled, succumbs to dementia, etc.