Maintenance Airframe; Maintenance Powerplant
Communication Breakdown; Confusion
Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Procedure; Company Policy; Environment - Non Weather Related; Human Factors
We were working a return from storage work card on Aircraft X; we were working off paper because the task card was going to be revised and it would have cleared all completed work if worked on iPad. The task card was revised and steps had to be transferred to a new task card. There were several technicians working the job so there were also working task cards for reference.  So there was the original task card - the revised task card and working copies to go through.I was the supervisor and assigned the upgrade [to the] Radios and Electronics Lead; xxxxxx step X electrical/electronics on task card; that step included de-preservation of emergency lights; aircraft battery; EPAS batteries and 'any other batteries' including flight attendant station emergency flash lights.At almost going home time for the technicians which is earlier than normal due COVID work hours nothing was signed off by the Lead; when I asked xxxxxx he stated 'it was all done' and they would sign it off.  When I was auditing the master paperwork step x.9 'any other batteries' was not signed; and all technicians had already left. I signed for the step as Supervisor since I was told it was done; I was going to verify that it was done but then got side tracked with other aircraft issues.The aircraft then position ferried with no flight attendants or passengers to ZZZ for a dead 'A' check where they found the flight attendant station emergency flash lights did not have batteries in them.No suggestion for resolution as I should have not signed it off without verification; I never have signed steps before without verification and will not again; however it could have been worse if it had been a revenue flight so the task card should include a flag; not serviceable tape; or some other way of visually seeing the flashlights did not have a battery in them; these return to service cards are something we have never done; the paperwork is extensive and made worse by the revision. I have used this as a reminder not to get complacent.
Supervising Maintenance Technician reported signing off work without verifying it had been completed.