Pls fix Render files going missing

Please fix this common complaint:

1. You render something.

2. You return to it later, or possibly move the rendered shot to another file, or possibly just move it with the timeline and then - horror - sometimes (not always) it needs re-rendering. Basically render files occasionally get lost.

3. If that is too difficult to fix (and it's something I have heard many people complain about over the years) then please have some kind of search function which would aid FCP to find the original render file with human assistance.

Thanks.

Harry.