BTA Sucked itself in?

[OkiNano]

I've had a BTA for over a month now in my 37g tank. Was out today and looked good. Got a new pump for my tank and did a water change. Now when I looked at it tonight i can just see its foot and it sucked its tentacles completely in. Is this a bad sign or do they do this from time to time? Thanks everyone

 

[finding nemo]

Very normal so don't worry about her, she will be back out when she gets her nap done.