I had an accident similar to your description when working as DM in Sicily (Favignana island), which occurred to a diver of my group.
He suddenly disappeared (he ballooned up).
So I did bring the other divers up with a proper safety stop, during which I was seeing the tank of the missing diver hanging below the boat, so I was sure that he had been rescued.
After surfacing I found that my wife was administering him pure oxygen and had already called by radio the coast guard.
The guy had minimal symptoms: one finger in a foot aching, possible due to the procedure of raising him from water.
However we played safe: ten minutes later I and the diver were loaded on a large rescue helicopter of the coast guard, which did fly us to the nearest deco chamber (at Ustica island), where the hyperbaric doctor recompressed the diver for a 6-hours oxygen hyperbaric treatment.
He exited the chamber with no symptoms.
The following morning he had a second, shorter ride in the chamber, and finally he was dismissed as completely healed, but forbidden to dive for the following 48h.
Of course we decided to play safe as we were in Italy, where all of this is entirely free (including being lodged and fed for the night at the firefighter station of Ustica).
In other countries the same trip by helicopter and two chamber rides could have been very expensive, so possibly people without proper DAN insurance would take the risk and not ask to be transported immediately in a recompression chamber...
! That's what I was looking for.
