There should be an indiciation that party invite is sent in the friend list

[Licho1]

Show for example little progressbar under player name to show if it has timed out or not.

[GoogleFrog]

Players with pending party invites have a blue symbol next to their name. Reopen if the symbol is missing.

[Licho1]

Ok i didnt see it in the friend list.

[GoogleFrog]

Is it missing there? Reopen and rename if it is missing in the friendlist.

[Licho1]

Yes it is missing from friend list