Thanks for the info Tomas
I don't seem to have a vision hat. Looking back a few saves, none of the other characters appear to be wearing it either. I may have had it at one time and got rid of it????
Brussian is L45 and found the room, so he should find the others at the same level. Except, of course, the arrow vanished when I moved him from the party.
With Brussian in place again, the blue arrow and therfore the secret room has remained vanished.
I bought the game within the last month so I assume it is the latest version.
Do you or does anyone have any other ideas? Besides the things to get, Djarma can get 51 HP according to the walkthrough. Not to be sniffed at.