There haven't been any support requests opened for problems with T-Shirts yet, but it's still early [UPDATE: SR#15289]. Plus, when looking at their ste, it has 4 links a user that needed help could follow. 2 of them, sends an email to email@example.com and the other 2 sends them to http://www.livejournal.com/support/.
Title on FAQ Page: T-Shirts / LiceJournal.com Store
Where can I buy LiveJournal T-Shirts?You can visit the LiveJournal store here: http://www.punctuate.com/sites/livejournal/
I need help with my OrderIf you have questions such as: Why cann't I use paypal to pay? Can I write a check? Why didn't I receive an e-mail confirmation? How soon will my t-shirt(s) be sent to me? How do you Ship them? How do you determain shipping costs? Why is there a man atop that flagpole with no pants on? etc.
You will need to direct them to Punctuate.com. That is the company LiveJournal has contracted to make the t-shirts. In addition to making them, Punctuate.com handles everything from billing and shipping to setting up and maintaining a LiveJournal.com store on their site for us. You can reach them here: Help?