Your file is most like still tagged, but your Bridge preferences are set so that they are not processing a preview on that large a file, so it appears as untagged. I'll bet if you open the psb file and choose the Show Color Profile dropdown at the lower left part of the document window, it will show the correct profile.
Dear p_d_f, You are correct; you won that bet: that dropdown you called my attention to does show the profile as Adobe RGB (1998). I'm so relieved. This had been frustrating me and confusing me a good bit. Thank you very much for your help. --Mark