1) remember to remove the loon's existing magazines as well as his weapon. Does removeallweapons this do that? Well, I can't remember.
2) The usual reason for this problem is a syntax error. In the Briefing our objectives are probably called OBJ_1 etc. If so, then in then in init.sqs you should have
"1" ObjStatus "hidden"
or whatever it is. If you called you objective OBJ_banana then it would be "banana" ObjStatus "hidden". It is NOT "OBJ_1" ObjStatus "hidden".
Hope that helps. There is a working example in the Tutorial Mission in the Ed Depot for you to copy and paste if you want.