Looks like regurgitated food.

To quote Deborah who just answered a post recently



Quote Originally Posted by Deborah View Post
When dealing with a regurgitation you need to wait TWO WEEKS and I cannot stress enough the importance of this.

After that it will either happen again or it will not

If it does you need to consider the followings

Bad feeder

Low temperatures not allowing proper digestion

Stress

Internal parasites

Based on your description it looks like the rat was not even in the process of being digested so I would have to go with the rat being spitted back out which is generally due to disturbance or size.

Either way because you have limited experience and your description may or may not be correct I would recommend to wait two weeks.