I am not seriously out of yarn ... am I?

I cast on for the dreaded first sleeve of the fair-isle sweater, as it has proved itself to indeed fit & not be ugly beyond all wearability.

I did the color work at the cuff, I got started on increases and... I finished my ball of yarn. Went to look for the next one. I've been stalling on this project for sometime, so I don't have a clear recollection of where the yarn was, or how much there was left, or anything like that. Couldn't find it. Now, I have a small stash, so it's not all that plausible that something could successfully hide in it. There just aren't that many places. I tried to look up my order receipt to confirm that yes, I had ordered a reasonable number of balls of the stuff, and I should not be out after finishing *only* the body, regardless of how much longer than specified I made it. Couldn't find the receipt. Couldn't find the yarn.

I guess I need to face the music. At least there is more of it on webs, and it's on even better sale than before. How much yarn does one need for a sleeve and 7/8 anyway?