I'm sorry, CC, I must have been mistaking your sitch for someone else's.
If that was never a firm boundary request, then I think it would be fine to wait several hours, and then respond with a "Sorry, just saw this. Crazy day! Thanks for the nice note, and hope you are well. CC"
I would hold back on an "I miss you too," as I think it sounds needy. If you want to include something like that, maybe a "Yeah, I've had some bad days along the way, but find I'm doing surprisingly well actually. Growth, right?" -- or some such.
