The first thing you should have done was upgrading slackpkg itself. What happened was that after the "r" letter, slackpkg was upgraded by the "slackpkg upgrade-all" command. Unfortunately, after upgrading slackpkg between Slackware 13.0 and 13.1 you will have to run "slackpkg update" again or else you get the checksums error and no further packages will be upgraded.
So, you ended up with a partially upgraded Slackware. the util-linux-ng package was not upgraded, and this is where the libuuid.so files have been moved to in Slackware 13.1.
The solution to this involves is not completely trivial, but I will try to outline what you have to do. First, you will have to have local copies of at least the util-linux-ng and slackpkg packages and copy them to a floppy or USB stick. Next you will have to have a bootable Slackware CD or DVD or USB stick.
You boot from the SLackware CD/DVD/usbstick, then do whatever needed to access the slackpkg and util-linux-ng packages (like, mount the floppy, or the usbstick). Mount your Slackware partition manually under the /mnt directory (if your Slackware partition would be "/dev/sdX" then you would run the command "mount /dev/sdX mnt"). After mounting the Slackware partition you upgrade the two slackpkg and util-linux-ng packages using the command "ROOT=/mnt upgradepkg slackpkg-2.81.1-noarch-1.tgz" and "ROOT=/mnt util-linux-ng-2.17.2-x86_64-1.txz".
That should allow you to reboot into your Slackware and there, run "slackpkg update" followed by "slackpkg install-new" and "slackpkg upgrade-all".