Do the surviving papyri disprove the Book of Abraham?

Egyptologists disagree, so we don’t know what the fragments say.

The Church essay acknowledges agreement on the point your friend raised. Egyptologists identify the surviving text as funerary and agree its characters do not match the Book of Abraham.

The fragments are funerary texts. What relationship did Joseph’s book have to those fragments?

You grant the evidence its force. A direct translation of those characters into the English book fails. Now consider how else the text may have come about.

Some papyri are missing. That leaves the possibility open, but it doesn’t identify their contents.

The survival of only part of the collection creates uncertainty. It supplies no direct evidence of Abrahamic text on the missing material.

Yes. Once you account for the missing portions, the historical problem is solved.

Missing material does not establish what it contained. The relationship between the surviving papyri and the English book still needs examination.

I can prove the catalyst theory from the surviving papyri.

A revelatory catalyst is one way believers account for the book. A funerary text cannot independently demonstrate that a revelation occurred.

I accept the Book of Abraham as revelation. The papyri could have prompted it, and the exact process is unresolved.

That states the Latter-day Saint conviction and the historical limit. You can then examine what the text teaches and why Saints value it as scripture.