You folks on larger instances probably don't see this, but often when somebody boosts a reply I can see the boosted reply but not the OP. (Original Post starting the conversation thread.)
This is because I am on a very small instance (mostly me) and not everything flows here. Understandable. Not a bug.
But I just discovered #Mastodon gives you a workaround: You can copy the link to the page of a post (hamburger menu, 'Open Original Page') with a right click.
Then paste it in the search box!