In the future ....

Most of my cameras have an accessory shoe. I usually tear off and fold up the end of the film box in a way that allows it to be wedged in the accessory shoe with a hint of the film type showing. Otherwise, 250sb's marker and masking tape is good.

If it were me, I'd go in the darkroom and roll it back to the beginning, look at it and reload and advance an extra frame (the beauty of the older cameras is that they are easy to fool when necessary!)