New BTA completely in rock?

So I purchased a slightly bleached BTA (LFS said it was from shipping) on Saturday. Day one was great, he looked lovely and bubbled up. Day. 2 he moved a few inches and slightly deflated but still seemed happy. Came home and he was really deflated, and almost completely in the rock. Decided to see if I could coax him out with food. He took the small piece of shrimp and promptly and quickly moved completely into the rock. He has yet to come back out. Is this normal for a new BTA? Thanks in advance :)

55 gallon with sump
SG 1.026
Temp 78
Nitrate 20ppm (trying to lower)
Nitrite 0
PH 7.8
System is 8 months old