Application portal reports an app as already installed even if it's missing from /Applications/

Symptoms

Application portal reports an app as already installed even if it's missing from /Applications/

Cause

Some files related to the app still exist somewhere on the Mac.

Resolution

Check /Library/Logs/pmm_appindex_agent.log for records like these to discover the location of the files and remove them:

10-15 21:06:56.455 D /pmm_appindex_agent:23937:307/ New 'app' available '/Users/kpavlov/Library/Mobile Documents/com~apple~ScriptEditor2/Documents/MacInfov1.app/Contents/Info.plist'
id = com.apple.ScriptEditor.id.MacInfov1
version = 1.0
10-15 21:07:12.698 D /pmm_appindex_agent:23937:307/ New 'app' available '/Users/kpavlov/Desktop/MacInfov1.app/Contents/Info.plist'
id = com.apple.ScriptEditor.id.MacInfov1
version = 1.0

or

04-24 09:52:57.063 D /pmm_appindex_agent:77:307/ New 'pkg' available
  '/private/var/db/receipts/com.ptc.PTC_FlexPLM_Config_TRAI.plist'
  id = com.ptc.PTC_FlexPLM_Config_TRAI
  version = 1.1