It depends on what they were doing with it. Jewelry, yeah I'd be pissed. Mixing with tin or arsenic, oh you better believe I'd be pissed unless the steel didn't melt. Beating it into tools, nah we're good, and I want more of this weird silver copper.
Actually I think the biggest issue here is that it's wildly unlikely a Sumerian metalsmith is able to actually do anything with steel. Their forges aren't likely getting hot enough to really do much with iron, and steel is way harder and less malleable than bronze. Maybe they can sharpen it, and depending on the shape they might be able to cold work it. It looks like iron forging was a few centuries away in Ea Nasir's time, and it required better tools, techniques, and forges.