I think you need the pharmacy records, not just medical records. Our provider writes scripts refillable for a year and DoDMERB wants to know how many times the script was filled. So, in the case of a DQ for inhaler usage, how many times was the rescue inhaler (or others) used? At least, that's my interpretation. If there are no records of the medication at the pharmacy and you said you don't believe you had any filled, you could request your EOB's from your insurance company to double check. I know when I called our pharmacy (it's a mail order pharmacy associated with our insurance provider), they explained that they would have to manually process the Explanation of Benefits to get that pharmacy information- we're still waiting a month later.
If there is no inhaler usage after 2014, your child should have a good case for a waiver because the DQ is for asthma after the age of 13... Your pharmacy should provide a letter stating that no prescriptions were filled during the requested period and I would submit that. My dd has the same DQ and has similar info. requested.
Good luck to you!