Can't get power to foglights on my 2003 Explorer

Likely there is a relay that operates the lights. I believe it is a relay that operates when the on/off switch grounds the relay, kind of like the horn relay. The relay may have lost a connection -- power in wire or ground wire to the on/off switch. Or the power wire into the relay or out to the lights may have become disconnected.
Try turning the lights on and off several times in a quiet location and listen for an electrical relay clicking. The under hood fuse/relay block may contain this relay. You'll have to trace wires from there until you find the lost connection, or bench test the relay with a battery and ohmmeter. Check fuses too. All fuses and relays will be identified in the owners manual or under the fuse block cover. G'luck.