Flyingtincan
I fly for RYR, so I can lend a word or two about 738's, but I cannot comment specifically on your experience. I hope I help.....
There is no such thing as a "short field take-off" in Ryanair, the concept does not exist. By that I mean we do not have any procedures for runways under a certain length. We calculate required thrust for the runway and our weight, and that is what we use. There is nothing we do differently if we are operating well below the limits or right up to the limits.
What we do do (if you'll excuse my English), is a "static run-up" for ice shedding on the engine fan blades when the outside temperature is 3C or less, AND if there is visible moisture (wet runway, fog, rain etc). Instead of spooling up to 40% and hitting TOGA, we spool up to 40% for 3 seconds, then 70% for 3 seconds, before releasing the brakes and hitting TOGA. This procedure does not have any effect on the take-off distance required.
Is it possible that this is what you experienced?
Wally.