Happens in Chicago on Verizon regularly, but reverts back to 2G (circle indicator, dial-up modem speeds). If you're lucky, it'll eventually go into 3G.
I have been having this same issue around Chicago with Verizon. Happens a lot in the loop, out by bolingbrook, up by Schaumburg and along the i-80 corridor. Sometimes it'll take 20-30 minutes for it to switch back to LTE.