Ask for a copy of the test results. Until you see the actual number, you are relying on their interpretation.
There is a range for negative, iffy, and positive. Under 3.5 is likely negative, but 3.6 would be maybe in the iffy zone.
You have to test right at the time of the problem to see what is happening. It's just like testing BG.... you may have a higher BG if testing right at ps, but if you test at +6, you can have a very lovely number.
Was the test done right at the time when you were seeing the problems?
Sometimes, you can just give pepcid, and it can help a great deal. One of my cats gets 1/4tab of a 10mg pepcid regular strength almost daily as she is gassy and has frequent pancreatitis issues. I try the pepcid first, and always have fluids and bupe on hand in case she is still having problems. My other cat often tests just over the 3.5 cutoff mark when he has normal b/w done, but he has no symptoms.
Hopefully the test results will show you where the numbers were when tested.