In the days gone by (pre 9/11) domestically that might not have been an issue. Internationally in the days when Snack Attack existed, again we were welcomed into the galley.
Today, you threatened their space and their security tasks. You could have been planting something dangerous in the drinks cart. I personally agee you were wrong.
Ding ding.. no answer.
I would then have walked up front to where the FA's were sitting and stood there and ASKED them for what you needed. If they groused (like cann't you see I'm on break) then you could have offered to 'can I get it myself'. The FA may or may not have agreed at that point.
I think your assumptive intrusion of their galley was wrong.
On 767-300 when I have been stuck on the EF side .. you have to cross thru the galley to get to the lavs. I make it a POINT on my first trip to the lav of locating the purser (or at least senior) and ASKING them if I may come thru the galley to use the Lav. 100% of the time I get an OK (mostly with a Thank You for asking) .. ONE time I got a 'YES as long as you wear shoes'. She then explained that there may be broken glass on the galley floor and did not want me to cut my tootsies. So of course I obeyed this request.
Personally had a more dominant matron been on your flight, I could well imagine you would be taken into custody at the end of the flight for 'interfering with flight security operations'. WOW would that have been a post!
KEEP OUT OF THE GALLEY!