That really does suck, I feel for you. Several years ago guys were going around stealing contractors tools, we had a whole 20' storage box emptied. Sort of feels like you got kicked in the **** and they didn't stop until your chest.
There are some serious chains and locks out there, but usually they are more secure than the thing you lock them to.
If you have one of those fancy phones that can go on the net, I am pretty sure you can set up that craigslist search to email you every new Logsplitter ad that posts. A friend of mine buys and sells, and has something like that set up so he gets the email almost the same time it goes on craigslist.
Best of luck finding them.
If you were closer, I'd let you borrow my splitter, but RI is little far for that.