There IS something wrong there. Even if Anna had seen it in the fridge she mightn't have thought anything of it. She might've even been told that methadone only comes in liquid form or some other BS.
Why would HKS leave all this evidence including liquid methadone in the fridge of the house and then leave the house unoccupied to go to FLA? Maybe the meth was a plant? "See Anna was a meth addict".
Or what if it wasn't really methadone in those bottles, but something else even more deadly? In which case, hks didn't expect the house to be broken into.