Regurgitation can be due to

Stress
Low temps
Internal parasites
Bad prey item / umproperly thawed prey item (if fed F/T)

Now just leave both animal alone, no feeding for the next 2 weeks, after that resume your regular feeding schedule and if this happens again consider taking them to a vet and have a fecal done.

Now the question was it regurgitation VS the snake disengaging from the prey and spitting it right back out?