What was the gravity reading? could it be krausen? Doesnt look like mold, not hairy enough.
It looks like a pellicle which is not mold thankfully. It might have been introduced in the glass. The is one way to find out, pull a bit out of the barrel and taste it. If it is infected than yes, the barrel is infected too and you can start your sour beer project now.
Seems unlikely that a pellicle would form in that short of a time.
I would not worry about your batch. Looks like something in the glass or airborne.I would imagine a commercial brew left in a glass would look the same after 2-3 days.