Hi countless,
U/S looks for abnormalities such as growths and changed blood flow and can also show granularity and other signs of extensive cirrhotic scarring but doesn’t tend to pick up fibrosis or inflammation very well. Gastroscopy looks for evidence of portal hypertension. That no issues showed up on either of your examinations is good news.
Fibroscan measures the stiffness of the liver and as you were a F3 this would probably have been due to a combination of bridging fibrosis and inflammation. Inflammation tends to resolve with treatment and the evidence from studies seems to show that for many of us the fibrosis will also decrease over time after successful treatment. Perhaps you can get another fibroscan in say 6-12 months to check?