If you look closely, you should be able to see your increases on the previous row, especially since you can narrow it down to a small area like the center of the piece.
Barring that, can you count your stitches and find your center knit st that way?
I would put in a lifeline now, and then do the best you can. If it turns out to be off a st or 2, then at least you can frog back and move it over a little easier.
"The cat has too much spirit to have no heart." -- Ernest Menaul