ITV3 should still be there on Freeview channel 10 (I've just checked mine). I have the full set of Freeview channels but I'm in line-of sight of the Crystal Palace transmitter. If you are a long way from the transmitter, you may be getting poor reception in the wet overcast weather - especially if the transmitter is broadcasting on low power.
Check that your aerial is pointing at the transmitter. If you're not sure, you can get a bearing using Google Earth. If you're out of line, you'll get poor quality on some channels and that might just be enough to stop your box recognising them. Then wait for a bright clear day (Sunday looks promising) and try retuning again.