I don't think the DEA or ATF is going to be coming looking unless you give them some reason to. The news stories of this happening are usually people who are suspected of doing something illegal anyway and OTOH you always hear news stories of someone finding a cache hidden in a house from where someone that lived through the depression mistrusted the bank and stashed away money or coins or gold. It seem to me that caches tend to get found by the next owner of the house rather than some .gov agency looking for it.