If you got shampoo in the phone, then it is still in the phone and probably the reason for your problem. That isn't something that will just dry up like say water. It would leave a residue behind which can cause problems.
You are going to have to, very carefully, get any and all of that residue out of the phone. There would really be no other way to get it to work correctly. And any left in there will start to cause more problems over time.