A Maintenance Supervisor did not follow-up to verify if Field Trip Mechanics received information to do a weekly inspection of the left hand main landing gear (MLG) door and adjacent fairing on one of their DHC Q400's prior to dispatch. Aircraft was dispatched without the required inspection accomplished.

Narrative

A DHC Q400 needed a weekly inspection of the LH Main Landing Gear (MLG) forward door; adjacent to the 'Y' fairing using a non-routine work card. Maintenance Planning called me the next day to ask why he did not see the inspection signed off. I talked to the mechanics when they arrived back from their field trip and contacted planning to inform them that; they never were told. The same Q400 aircraft was broken in ZZZ and a Mechanic was down there to fix a different write up. I contacted him and he completed the inspection there instead of ZZZ1. I was busy trying to get the mechanics set up for the road trip and multiple other aircraft that were broke for the same reason. Planning called and wanted the inspection completed at ZZZ1. Because the aircraft was staying there that night for fuel temperature problems; I thought I told some one to pull the non-routine work card; to give to the mechanics and to take extra tape with them. I was so busy I forgot to double check to see if they got the word to do the inspection.