AITA for using my sibling's special paper?
This had me and my friends perplexed so I wanted to get others' thoughts. Details changed for privacy. Also advance apologies for formatting I'm on mobile.
I (35 F) have a rocky relationship w/ my family, esp my sibling (30 NB), Z. Z's hobby is art. I used to draw but quit early on.
Days ago, Z texted me asking if I used their special paper for my post-grad work. I didn't remember and asked for pictures. Z sent pics of diagrams and notes written on the sheets, lamenting that expensive paper was wasted and "it's like you gave a toddler Copic markers."
Context: The reason why the papers came about is because Z recently got into charcoal art and looked for more paper in the garage, where we store a variety of art supplies accumulated over the years. Z doesn't work + lives at home, so my parents support them and would have bought more if they had asked.
I vaguely recognized the notes from a specific HIGH SCHOOL program I was in, but didn't remember using Z's paper. I told them incredulously that it had to be at least 2 decades ago. I suggested that our parents probably bought us both papers as kids, or maybe Z wasn't using them anymore so our parents gave them to me. I really don't know. Z realizes one bundle of sheets is indeed mine (has a note directed to me on it), but still insisted that I must have stolen the other papers from them or should have known better than to use nicer paper even if our parents gave it to me. I told them I genuinely don't remember, I was 15?
By now I was even more irritated and said that this was 20 years ago: neither of us know the context and their frustration is misplaced. Z countered that they thought it was more recent. But even if it were during my post-grad as they initially assumed, it would've still been at least 8 years ago. I think most people wouldn't be so upset when NEITHER remember after so long. Z thinks I do remember and am denying it. This goes back and forth with me emphasizing my bewilderment that this happened 20 years ago and Z saying they still remember everything when they were 15. Z says I'm rude to family, gaslighting them, and unempathetic to others.
I offered to buy new papers but they don't want them. We haven't spoken since then.
I'll admit I probably came off irritated because Z and I already have a complex relationship. I just don't think I need to apologize when neither of us know what happened. My partner agrees my sibling is irrational but thinks I could have just grayrocked instead of being stubborn. I do tend to have less patience with my family because of past conflicts. AITA?
EDIT: for some more context and also to add, we do not have beef because of their gender identity. I am also queer.