Hi Jack,
Try this:
Find any post from your old username
Select the username at the top of the post
In the pop-up menu select ”View Forum Posts"
That should bring up ALL (338) of your old posts.

A more efficient way might be to use"ADVANCED SEARCH"
Touch the Magnifying Glass
Select the "Search Multiple Content Types" tab
You can enter a user name AND keyword(s)
)BOB