What do you mean by "figure out" exactly? You mean because you always append something to the original URL, like “_thankyou”?
Yes, exactly. We have many different webinars and are currently just using an append like that
Well, nothing stops you from generating a GUID instead and using that as the Thank You page’s URL, no?
Unfortunately, if your Thank You page is a non-Marketo page (I assume they’re non-Marketo if the LP is non-Marketo?) then you can’t use Marketo’s ability to expire local assets on a certain date. Otherwise, you could set them to time out. Your CMS may be able to do the same thing, though.