I have flown without ID before. You get SSSS and magic wanded, but aside from that, it was not a big deal.

Once, in LAS, I lost my license at a casino. I was able to fly on to SFO with no issue. (I actually could not check into the hotel in SFO, but was able to stay at a Club Quarters, as checking in at their self-serve kiosk saves one from needing a license.) I was then able to fly from SFO back to Atlanta the next day, again, with no issue.

A third time, at MDW, security was very backed up from all the WN passengers. There was an earlier flight that I could barely make, so the gate agent actually suggested I hide my ID (will not disclose which airline) and then took me to the front of the security line because I needed special screening. I made the flight.