Would a completely normal liver ultrasound and a normal fibroscan/cap result, rule out fatty liver in a patient?

Not entirely: Fatty liver occurs thru delivery of dietary fat/fatty acids to liver, excess carbohydrate, impaired export of triglyceride from liver cells, & augmented trigylceride production. If at risk, or NASH is suspected without biopsy confirmation, fix it by controlling diabetes, obesity, cholesterol, & avoid alcohol.

Not a 100%: But nearly so. Cases of hi liver enzymes with a normal sonogram are. Frequently hepatiyis E

Mostly ...: Remember the fibroscan is looking to measure fibrosis. Not all fatty liver disease causes fibrosis, this is more of a late stage manifestation. But a normal liver ultrasound should give you some reassurance. The only way to really now if there is any form of fatty liver disease, is by undergoing a biopsy. This often isn't necessary though. Please seek further input from your hepatologist.