Page('pagetitle/key:value')->url() results in error

Error:

Call to a member function url() on boolean

I can access the page pagetitle/key:value without problems

any suggestions? is it just not possible to apply the url() method to a slug, that contains a filter?

Edit:
nevermind, I hardcoded the filter after the phpcode

To answer you question: no, this is not possible. The page helper only takes a page URI as argument.