Yer basically right, and because I couldn't stand it any longer I went into the trash or the back up. or both, and got the one set of non duped imported dng, and the set of cr2 all of whose names had been altered to match, and put them in the appropriate folder on the HD. And like magic, the dreaded exclamation point on every single picture in that folder in the catalog vanished, poof. Some minor developing i did on one file is gone, but the tags remain. So I'll live with this for a while [certainly too soon to claim victory over LR] and hope that these problems, which were restricted to these 191 shots in 1 folder, never darken my door again.
Thanks for your help, time for another adventure. Stay tuned.