Thanks for the tips, ladies!
Jan, mainly I wanted to know how to correct the situation on future projects, as the closed buttonhole isn't the only flaw in this cozy. It ended up way too short for my cell phone, though the width and snugness of it was good. I'll have to do some adjustments if I decide to attempt the felt pattern cozy again.
Meanwhile, I knit one in Sugar'n'Cream cotton (lime green) from the pattern in the Stitch'n'Bitch book, and it turned out great. I did have to go down a few sizes in needles from what the pattern called for, as well as adjust the length of it to fit my cell phone.
Someday, I'll figure out how to post pictures. Meanwhile, I will probably need another computer first, as mine appears to be very, very ill :verysad: (I'm on my ds's at the moment).