Yes . . same thing happened to me . . would like to hear about the solution. I ended up downloading another contact/phone app (GO Dialer Ex), but would rather just have the original phone app/icon on there.
To install the dialer.apk, download a file manager like Astro.
Enable non-Market downloads by checking Unknown sources under Apllications in settings.
Copy the dialer.apk to your SD card.
Open the file manager and navigate to the file on your SD card and select it.
A message should pop up asking if you want to install it.