A few points…
1. This is the promo-nation website. It's a group of Vendors/operators from around the country who are nice enough to offer you a chance to win other prizes than the monthly IT(Incredible Techonoligies, the maker of Silver Strike Bowling) prize.
2. This site is up to date. The current Promo-Nation bowling contest runs from September 8th – November 8th. Those prizes listed are for the whole 3 months, not awarded every month.
3. The link you've posted http://www.silverstrikebowling.com is the actual game website(set up and maintained by Incredible Technologies). So the $3000 Home Depot gift card has nothing to do with Promo-Nation, therefore has no reason to be posted on this Website. That is the monthly raffle prize awarded by Incredible Technologies. If you'd like to know about what IT is giving away for the monthly prize, you'll have to check there.
4. If you looked around their website a little harder before coming on here and shooting off, you would have seen they have the prizes listed for Nov and Dec.
http://www.silverstrikebowling.com/ssb2/SSB/Sweepstakes/Prizes/