The title says it all:

[Linked Image from i.imgur.com]
The action point isn't spent, it's just the ranged sneak icon is disabled. Game version (was in the top right corner): 4.1.1.1311526.

I've only seen this once, after picking Astarion for the first time and levelling him to 4, but I wonder if it's a glimpse of a new future "homebrew", or just a weird bug.