I also have both versions installed. IIRC the 64-bit version's icon will say "Sonar 8.5 Producer Edition (x64)" ( I shortened Producer Edition to PE so that I could read which was which--otherwise it will say "Sonar 8.5 Produ..." for both until one is highlighted.
I also changed the icons to further distinguish which was which, and altered the splash screens (adding "32-bit" to that version, etc.).
I installed the 64-bit version first, and I'm pretty sure it said x64 even when it was the only one installed.
Another way to tell: right-click on your Sonar icon, open the Properties window and click on "open file location". If it's in Program Files (x86) it's 32-bit. 64-bit would be in Program Files.
Hopefully this will clear it up.
BTW, why did you uninstall--whichever version you uninstalled? They can both coexist peacefully on the same machine.