Gamers are among the savviest users. Many have bright coding skiils and deep knowledge on how things work. That is a good customer base to deal with. On the other hand many tend to remain "invisible".
That is a challenge for Marketo and most applications interacting with prospects and customers.
One suggestion is trying to reverse the IP of randomly selected leads. geoiptool.com is a good one. Some may be in genuinely unusual locations. The remaining would be behind proxy networks such as Tor. Identifying 85% or so is an interesting challenge. I am happy to join the cat and mouse game 🙂
I have also tried (on the php file) running the script within itself with $.getScript for Munchkin and in there the function to associate the lead and track the page view. This to make sure it was fully loaded as it's a callback.
The only way the 'old' script works if some physically visits the php file (e.g. if it would be loaded in a 1px frame). But in my case the file is loaded with $.get within the javacsript of the game.
The techniques already in place are very clever. That is becoming an interesting puzzle.
One potential issue is the usage of ' or " in some of the parameters being sent via the associateLead call. This can sometimes close a parameter inappropriately and cause the call not to execute. You should look into setting the variables prior to execution of the call and URL encoding them to prevent closure of your parameters.
Another possibility is if you're calling associateLead prior to a new page load, the new page may be loading prior to the call execution finishing.