You say there's only a limited number of places it could be, and only some are active on any particular day, with that information "out there". I'm thinking race-courses.
So you're not trying to find the scanner after it's been stolen
In fact, you don't even want to know where it actually
is, just where it's supposed
Could you put the information on a server somewhere, eg. google sites, and have your Pi access that? It knows which scanner it's embedded in, and what day it is, so it can find out where it should be.