[kmike]

Also, I don't truly believe that anybody gained access to the database.

Then how did they selectively deleted the data from some tables and not the others? If they used vBulletin "delete user" feature, all user data would be gone.
You also can check some other secondary tables like 'subscribethread', 'subscribeforum', 'editlog', 'deletionlog', 'moderatorlog', if there are some records with deleted member's userid, it'll be another proof the attackers have a direct access to the database.

I also don't understand your priorities, ignoring the issue of someone messing with your database with malicious purposes is on the verge of light-mindedness. You can't even really tell if your database is still intact! They could have already altered or deleted some small things here and there. I understand that you only found that the member's posts are missing because he's a high profile member and a mod. Who knows how much more data is missing?

If anybody has a more simple method of getting all his user information back into the database - possibly step-by-step instructions just in case I happen to get lost - I'd really appreciate that. Really, I would. Thanks!

There's no simple step-by-step instructions for your case because you don't even know what data is missing. But generally you can use my instructions above for all tables containing "userid" field - you can find them by searching mysql-schema.php in your /install/ directory. And then running "LOAD DATA INFILE '<table>.sql' IGNORE INTO <table>" for each data file (note the "IGNORE" keyword, it'll skip the rows with duplicate primary key, i.e. those that already exist in the main database).