Setting Off RFID Alarms: Causes & Solutions

[WWGD]

Hi, I am almost completely ignorant on any Physics beyond the high school level. Not proud of it, but it is a fact.
But I am curious about this:
While at a bookstore, I set off the RFID detector. I found out, by trial and error, that (something in) my wallet was setting it off, but not clear on precisely what. The security guy deactivated my wallet at this point , and then the wallet stopped setting the alarm off. **BUT** a few days afterwards, the problem reoccurred, i.e., my wallet set off the RFID alarm again . This seems to imply that something I did in the meantime, after deactivating up to the second alarm, may have reactivated the RFID signal, or possibly some chip in my wallet ( I don't think the one in my shoulder was setting things up --ha-ha).
What possible explanation is there for this, assuming the alarm is working reasonably well ( which does seem to be the case.)
Thank You in Advance.

 

[berkeman]

I had a similar problem with a wallet a few years back. It would only set off a few of the detectors at the mall, but it was pretty annoying. I finally found the very thin RFID tag stuck between a couple layers deep inside the wallet. Maybe see if you can dig your way far enough inside to get to it. Otherwise, maybe ask the same place to try deactivating it again. In general that blows a diode, I believe, so it should not self-heal...