Lost pet evolution tier progress

Unrelated to event I replaced my pet trainer and it has removed all my pet progress after it states it wouldn't do that then tried to put back in old trainer but won't let me is this a bug? I tested it out because others were curious but didn't want to risk losing there tier progress of pet so after reading the description I thought it wouldn't so I tried but it seems to have removed my tier of pet and progress and won't let me put back the old trainer in it to tier it back to t7

Can we please get this fixed when possible

I think I see what happened.

The UI showing tiers of previously unlocked trainers and allowing selection without having one in inventory had mistakenly not gone out, so that is fixed if you patch.