This is quite possibly the rudest person he's come across so far, excluding himself. Being set on fire in a public place would be more than a little attention-grabbing, but he can't exactly let this guy just walk away when he clearly has important information Zim hasn't managed to siphon away yet.

"HEY! We weren't finished!" He yells after Taako, hopping off the table to follow after him, abandoning the broken scanner. This is more important than having more equipment he can take apart and put back together and besides, scanners are easy enough to come by. Weird nonhuman things with knowledge of why his brain is more messed up than usual? Infinitely more valuable.

"How is any of that important?? Don't you have those memories?!"