Oops -- deleted swap files (Mac OS, 10.6) -- will they come back?

To re-create swap files, you should restart the Mac (a normal shutdown is all that's needed). Swap files get cleaned up each and every reboot whether you attempted to mess with them or not.

I used the word attempted since you can't really delete a swap file from under the system due to how unix (the underpinnings of Mac OS X) works. The best you can do is remove the entry in the filesystem that points to the swap file, but any file doesn't get deleted until all files that were using the file are done with it.

Since swap files contain the state of the machine while running, they are marked to not be backed up since they change from second to second and get recreated each boot. To back them up would simply waste space on the backup and time of the system.

You picked a good system file to delete - next time be sure to ask first before deleting other files since many system files are not as forgiving when you delete them from a system and then reboot things.