You might be able to recover them, but not too sure and it might not be a flawless recovery due to the change to the anon user at deletion. I'd recommend doing a backup before getting into tis.

First thing you're going to want to do is run the following query:

SQL Query
select count(*) 
from ubbt_POSTS 
where POST_POSTER_NAME='username'

Change username to the name in question and hopefully that will come back with the proper number of posts for that user. Make a note of the number that was returned.

If that comes back with what looks correct, then what you'll want to do is create a new user with the username that was deleted and then jot down the userid. At that point, you can run the following queries:

SQL Query
update ubbt_POSTS 
set USER_ID='userid' 
where POST_POSTER_NAME='username'

SQL Query
update ubbt_TOPICS 
set USER_ID='userid' 
where TOPIC_POSTER_NAME='username'

userid = the new userid that was created
username = the username in question.

Then you can run this query:

SQL Query
update ubbt_USER_PROFILE 
set USER_TOTAL_POSTS='postcount'
postcount = the number that was returned from the first query.

That should reattach the posts to the new user that was created and the post count should display properly for that user. Like I said, do a backup first just in case you run into any issues.