I ordered a barrel in Nov 2017 and received a confirmation of the order via email...and then another email when it was delivered.
I've also sent a message from their web site with questions and gotten a response (try info@DIAMONDBACKFIREARMS.COM ) the next business day (I sent email on a Saturday, they responded on Monday).
Did you save the info from the order (order #)? If so, email them with the details.