If I had a small bowel obstruction with a closed loop and herniation in to the omentum, what is the likelyhood it could happen again?

Unlikely. If you had surgery, which i assume you did, the chances of a recuurent bowel obstruction are low but possible. It is very infrequent that people require multiple surgerires for recurrent bowel obstructions.
Recurrence of SBO. Any small bowel obstruction has the potential to recur, even after surgery. Persistent signs and symptoms should be followed and investigated if severe.
Good if not fixed. If you had surgery to repair the herniation, then the omentum was likelysplit and it is unlikely to recure. If it was treated conservatively non-operatively, then it is likely to recur. Often the small bowel loops are scarred down or adhesed to the omentum and if there is a hole in the omentum its only a matter of time before things re-herniate.