Most likely you just killed half the yeast by not re-hydrating... which translates into a longer lag time as the yeast multiply to make up the difference.
If it was a high gravity beer... above 1.070 or so... the yeast damage may have been even more.
So if you have another yeast packet, pitch it and you will be fine. If you do not, wait a day, and you will "probably" be fine.
Good luck