This might be the source
Or maybe this
Actual there are thousands of them just try a search on the Executive order 6012 for it did happen once and I am assuming from your question you did not know this. Maybe I misunderstood your question.
No, that’s not a source.
Classic example of why people need to source PRIMARY sources and documents. There are copies of the original order available through .gov in .PDF form, there is no mention of silver confiscation (duh) nor anything about safe deposit boxes. Most people back then learned of it at their Post Office, on a large poster with the text of the executive order.
Austin rare coins just wants to scare people into buying numismatic coinage under the implication that those types of coins wouldn’t be stolen for some reason, and without regard to that are posting bogus versions of presidential XOs. Pretty scurvy.