Is there a 2x12 size Lego Brick?
There used to be 2x12 bricks a long, long time ago:

There are plenty of legacy parts that aren't included in LDD, and it looks like this is one of them.
This part dates all the way back to 1954. I don't think that they've been used in a set since then, and I don't think they were updated to use tubes on the underside or to not have slots in the end. I don't personally have any of these, but I'd also guess that they were never released made of ABS.
That's the answer to your question, but to help you solve your problem, it is often useful to use large Technic beams when building the framework of a large structure. These are long, sturdy, and can be pinned together to form very long beams. You could pin together 2 2x12 beams in order to get the brick that you're looking for. Technic beams come as large as 1x16, so you can create some really nice beams with these.