The problem lies in the way officers classify searches. Where an officer is conducting a search for weapons such as knives, but finds drugs instead, the results are recorded as a positive search for weapons.
As a result, the recording system has given the impression of 1506 more weapons finds than there actually were in the force's first year.
MSPs hit out at the "misleading" and "dodgy" figures.
Stop and search is a tool strongly associated with Police Scotland Chief Constable Sir Stephen House, who rolled it out to the single force after using it extensively at the old Strathclyde force, which he headed.
But a number of flaws have emerged. Police Scotland's end-of-year crime report noted the total number of detections of offensive and bladed weapons - 3,712 for the first 12 months - was 1,506 lower than the number of "positive searches" for the same category.
Scottish Liberal Democrat justice spokeswoman Alison McInnes MSP said: "For months I have challenged the Justice Secretary on the dangers of unregulated stop and search and time after time he has relied on these dodgy figures."