I seem to never have that problem since my ground maintenance crew can find and maul a sprinkler head under concrete.
I have, though, upon occasion simply shoved a fish tape down a lateral, hooked up the 521, and traced to the end painting a series of dots along the way. Then backed up and probed for the head. Tried turning the section valve on first but the head was buried too deep.
That's an awesome solution I'm writting that one down for those pesky hard to find spray heads.