Hi vajim,
Ah, I think you’re referring to a STICKER that is placed on the bottom of your mattress with a bar code and a number? That is something Sealy does for tracking and for potential warranty issues.
The larger tag you’re referring to is the actual law tag, and it is normally sewn into the tape edge of the product near the head of the mattress. If yours isn’t there, I can only assume it has been torn away throughout the years. Sometimes you can find remnants of it in the tape edge/welting.
If you’re eventually going to start looking for a new mattress, be sure to start your research with a good read through the mattress shopping tutorial here. I’ll be happy to help with any new questions you might come up with.
Phoenix