Thanks so much for this pointer. Even though I had linked, etc. my accounts before the merger, when I finally logged in today to check on things, all of my SPG points, nights, and status were gone. I couldn't log in at all on the web with my old SPG credentials. After seeing your post, I tried the app, and was able to get my new MR number linked to that account and see my correct balance. I still can't see anything on the web, but I feel a bit reassured now. (I've been on hold with Customer Service for 30+ minutes now, btw.)

ETA: Aaand, I've just gotten off the phone with them, and the agent couldn't do anything to merge the accounts. Normally, I'd HUCA, but not with these call volumes right now. Hopefully it will be resolved by next Monday when I need to actually use my status.