The stories were initially panned out by Thomas Gets it Right writer, Robert Rigby, credited as Robin in the latter's end credits.
Robert's episode of Thomas was called Thomas Gets it Right. Our archives reveal that the two episodes he wrote for Jack and the Pack were called Safety First and Treasure Hunt.
But I'm afraid neither Robert, nor we can remember whether either was produced. As said, this was a short-lived spinoff.
It is not known what the plots would have involved. Whose the Boss and No Dozer is an Island also met the same fate.
Thanks to SteamTeam.