Pet store Gerbil

[(Sarah) (Churchman)]

Hi!
Today I was in a Pet shop, it is a major chain here in the UK that has put a
lot of independent "better" stores out of business, I think those in the UK
will know who I am referring to!
Anyway I was checking out the gerbils as I usually do and there was a gerbil
in a tank by himself, by his size I was guessing he was no more than 4 weeks
old and he was really hunched over like he was dehydrated.He looked awful and
I don't know how long the staff will take to realise he is ill, I only know
from seeing it in my own gerbs.
Is there anything I can do?
I think here the RSPCA only check whether the animal has food, water and a
clean cage which this gerbil does!
Please advise! I feel like buying him becasue you get a free helath check at
a local vet and the store pays but I really don't want any more gerbils right
now.I have heard terrible storeis about them taking the sick ones out back
and killing them or even worse leaving them to die!
Thanks
Sarah