Thanks, the stay has appeared again and credited now, not sure if was due to my message to IHG CS or if it was just very slow.

As I've only done award stays with IHG during the pandemic, I didn't know that nowadays it takes a long time for paid stays to credit. Mostly been staying at Hiltons where all stays basically post within 24 hours... but it was a bit odd that all trace of this stay was gone, and missing points form said it wasn't a valid confirmation number.