The bug strikes sometimes, but not always; hard to say what's going on in the backend. I've lost stamina to this too, but it'd take a bigger bug than this to ruin my mood after I got Toad Lilly from the new 10+1 roll.

Also:

Gather section Stamina incident

Saturday, May 14th 2016


Hello,
We have received reports of incorrect stamina result after going through a Gather mission.
We are investigating the issue during this week-end. If you are experiencing problems, please report them via a Customer Support Ticket or on the #issue_reports chat channel( don't forget to give us your Nutaku ID). We will update this page with more information.

We apologize for the inconvenience,
The Flower Knight Girl Team

Looks like the devs are on it.