It scans just fine here in REAPER ( 6.23 ). Have you tried: options > preferences > VST > rescan... > plugins that failed to scan > select offending plugin ? It might just scan on a second attempt.
Also, it is possible to manually edit "C:\Users\Username\AppData\Roaming\REAPER\reaper-vstplugins64.ini". A valid entry will look like : Rand_x64.dll=82B612B143F9D601,1382116964,Rand (Sampleson)!!!VSTi.
If it's been rejected like: Rand_x64.dll=82B612B143F9D601.
To force REAPER to accept a ( working ) plugin, just add a 10-digit number that's not already in use and the name/dev/type tag as above