Daniel,
I added the line as you suggested, but still got the same result.
To simplify things, I've taken the status check out of the module, and stripped it down to the bare essentials:
exten => s,1,NoOp(*TEST* ${CALLERID(num)})
same => n,Set(__USEROUTCID=${CALLERID(num)})
same => n,Dial(Local/15555555555@from-internal/n)
same => n,Hangup()