A DC9-30 WAS DISPATCHED IN NON COMPLIANCE WITH GEAR PINS INSTALLED AND NOT REMOVED PRIOR TO FLT.

Narrative

I COMPLETED THE OVERNIGHT LINE CHK ON ACFT X AND WAS PREPARING TO GO INSIDE AND FINISH THE PAPERWORK AND ENTER IT; WHEN THE MAINT MGR CALLED AND ASKED IF WE COULD BRING IT TO THE GATE ASAP FOR A FLT. THE ACFT WAS NOT SCHEDULED TO FLY UNTIL THE NEXT DAY; BUT I TOLD THE MGR WE WOULD FINISH THE PAPERWORK AND BRING IT TO THE GATE. TECHNICIAN Y WAS WORKING WITH ME AND ASKED IF HE SHOULD GO OUT TO THE PLANE AND DO THE WALK AROUND; I SAID NO THAT I WOULD DO THAT AND FOR HIM TO PICK UP THE LOGBOOKS AND MEET ME AT THE PLANE. I WENT TO THE COCKPIT AND PROCEEDED TO READY THE PLANE FOR TAXI. TECHNICIAN RETURNED WITH THE LOGBOOKS; AND WE TAXIED TO THE GATE. WHILE SIGNING OFF THE PAPERWORK AND LOGBOOKS; TECHNICIAN Y SAID THAT HE SIGNED OFF THE LNDG GEAR PINS. I BELIEVE NOW THAT TECHNICIAN Y HAD SIGNED OFF REMOVING THE GEAR PINS; BECAUSE HE THOUGHT THAT SINCE I HAD COMPLETED THE WALKAROUND; THAT I HAD ALREADY DONE IT; WHEREAS I THOUGHT THAT SINCE HE HAD SIGNED THEM OFF; HE HAD REMOVED THEM. THE FLC DID NOT SEE THE GEAR PINS ON THEIR WALKAROUND; AND THE PLANE TOOK OFF. WHEN THE LNDG GEAR WOULD NOT RETRACT; THE ACFT RETURNED TO ZZZ; HAD THE PINS REMOVED; AND CONTINUED ON WITHOUT FURTHER INCIDENT.