Can an IBD (specifically Crohn's) only show up on a biopsy?

Hey everyone, I'm new here! I've been experiencing severe upper GI reflux symptoms for many months. To the point I couldn't speak for weeks due to all the acid. They did an upper GI endoscopy and found inflammation in my esophagus and lesions on my duodenal stomach. Negative for h.pylori. Since the procedure, I developed super bad lower gi symptoms. Diarrhea for 14hours straight, just sitting on the toilet. Severe abdominal pain and cramping where I would wake up in excruciating pain and just lay on the floor. The doc immediately got me in for a colonoscopy. He said the lesions found in my upper GI look like Crohn's lesions but he needed to be sure. Well, visually my colonoscopy didn't find anything. I'm wondering how common it is or if it's even possible to find Crohn's ONLY in the biopsy?!?? He told me before I even got the colonoscopy that if we didn't find anything we'd try the pill cam, but I'd rather not have to pay for it if there's no chance of finding anything. Thanks for all yall do 😀