That's why I always advise against fake plants in the tank, I found that out the first time I put fake ones in long ago, my dragon tried to eat it, too. But don't feel, bad , a lot of people do use fake plants so it can happen, don't beat yourself up.
It might be best to have an Xray done to see if it's a large amount or small. A small amount could be passed through almost certainly. You'd just feed him smaller amounts but add natural laxatives like applesauce, baby food squash and veg. oil to help lubricate it through. Feeding him smaller amounts would help his digestive system to keep moving but not add too much bulk if he is impacted.
Exactly how big is Civ ? A big dragon can pass lots of junk.