This seems to be the handbook for price complaint inspections following a complaint to the relevant authority (in this case, the Maryland Office of the Attorney General).

https://mda.maryland.gov/Documents/HANDBOOK%20130%20Examinat...

Practically-speaking, stores have at least as long as it takes for an inspector to come out to the physical location. So, yes, it's a bit of a loophole, but I imagine that if you're mispricing as a matter of course and getting hit with complaints and constant inspections, you're probably going to eventually get fined (unless you're paying off inspectors). Store operations are usually designed to catch mistakes, as half the job is making sure items are stocked and labeled correctly. (I think most stores would prefer to transition to essentially local warehouses that delivered to customers from online orders, so that they wouldn't have to deal with any of this, but then they'd lose out on impulse purchases.)