To give an unorthodox answer: if you're unhappy that you spent time reviewing the paper, and feel frustrated that the review request was canceled, one idea would be to look around the Web to check whether the paper you were reviewing has been posted publicly online as a preprint.
If it is, then in principle you could have discovered and read it by yourself. So you could try to use the reviewing work you already did to some benefit, e.g.:
- give some private feedback to the authors (e.g., if you found mistakes, to point out relevant work, etc.); or
- post an open review of the paper somewhere, in the spirit of open peer review
Of course, some additional efforts may be needed: reviewing for a journal anonymously is not the same as directly contacting the authors or posting the review publicly in your name. So you'd have to work more on this, which you'd have to see if you are interested in doing.
To be fair, what I'm proposing here is somewhat unconventional, so maybe there are reasons not to do it. But in my opinion, if you already did substantial work on the review, it'd be a shame to have it go to waste and these are options to put it to some use.
(Come to think of it, what happened to you is a pretty good reason to only accept to review work which is publicly available as a preprint, so as to ensure in advance that your work won't become useless if the request is rescinded.)