Should have had something
If it was a sealed box you got, then it should have also come with a manual who's first page or two should have listed out each item that should have been included in the kit. I believe the 4 cell AA holder is supposed to have been in there, it's what came with my 5308. However they are a pain in the butt. They hold the batteries very tight and if you land hard on the nose or tail, the batteries shift and break contact, meaning you now have to shut down, pull the cover, adjust batteries, replace cover and go again....at least while it's new...after a few scratches and bashes, you'll just pick up about 4 feet in the air and drop in all four to seat the batteries again. In either case, get a receiver pack and install it. it will be the last time you pull that cover off to mess with batteries again. Well worth the couple of bucks it takes for the batt and charger. Make sure you get the right one. i almost ordered a sub c pack by mistake and fortunately was saved by this forum. Also different models of revo's use different packs. my 5308 uses a 5cell flat pack and fits perfectly even though the manual shows a hump pack. If you have access to a LHS, just take your car in and make sure what fits before purchasing.
Being in Iraq, the LHS is out of the question. So, once again HUGE shout out to the great guys in this forum. Have saved me from myself on more than one occasion.