If you really wanted to keep track of a card, you could have some sort of portable security system like stores do. Put a sticker on your graded slab and if you don't deactivate it, it goes off as soon as it leaves your area and sounds an alarm. Yes, stickers can be removed, but if it takes someone 3 minutes to take off a sticker within 10 feet of you, it is less likely they will spend the time doing so.
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Actively bouncing aimlessly from set to set trying to accomplish something, but getting nowhere
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