yes it was wrong....I went to a Presbyterian church when visiting extended family and I did not partake of the “communion”....I think it disrespectful.....I assume that others study and prepare for their communion as I would mine.
Would it be wrong for a Catholic to take Communion in a Baptist Church? If this “cross communionism” is wrong then it should be announced prior to handing out the crackers and grape juice.
I did the same at a Lutheran church, above the protests that I should just do it. Wasn’t sure what the requirements were.