When u lost a quest item, i think you should do that quest what gives you that item again. Sometimes it works.
If not, than you should contact an active GM about it.
Next...When your pets killing a monster it not counts. You need to kill it by yourself than it is counting.
Next...Leone is right. When you have a full bag and you bought something, than it can not be shown in your bag, because its full. Try to make 1 r 2 spaces and relog. try that 2-3 times and should appear in your bag. If not than take a look in your other accs what r connected with you gmail. Maybe it has been transfered into them, because of the full bag.