Although I am unsure about having NLR in Bank, you did enter the Fountain District to cross through it. As stated by the rules you cannot enter the district you have NLR in regardless of what your purpose is there. There are a few exceptions however crossing through the district is not one. I do not believe a warning was needed but it is most definitely valid.
EDIT: After quickly reading through the appeal again I'm a bit confused: you got NLR "after a warn and being rocketed" - does this mean you received both a warning as well as a slay? Considering the fact that slays have nothing to do with RP you should be allowed to re-enter the district as the NLR is for RP and slays are not.
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