it's quite possible for a letter check to be signed in the log book without that person doing any work on that aircraft. Generally signing the log book letter check means that the paperwork and taskcards have been correctly signed off and the logbook review is ok. Obviously this changes from compnay to company. Why not ask the person involved to explain it to you. If you make an unfounded complaint through ignorance you won't raise your popularity stakes. Noone minds questions being asked in the pursuit of knowledge!!