Not sure how to handle this

So I join a lot of Facebook groups for Disney and TV shows and I have an old Facebook I joined a few on that my main is also apart of. I’ve done that because I don’t want my name attached to certain posts since people I know are in the group. There’s no anon option.

On my old Facebook I’ve made 2 posts in the group one of them within a week. It has a random photo that I love as the profile. I don’t ever check messages on it.

I got a message from the admins. My main Facebook they asked if my old was me. Second account they tagged my post and said they were messaging me and to check it. That message was asking about my profile photo.

What do I do? If I deny it on my main Facebook is that a dead giveaway?