Actually, you can google it, as long as google has indexed it (may take a couple hours)
on Google, search for
bitcointalk.org: (unique phrase in your post)
For example, I can see all posts that quote my collateral post by typing:
bitcointalk.org: "Collateral is something that can easily be resold to cover the loan value plus interest should the loaner default on the loan."
(note the quotes)
https://bitcointalksearch.org/topic/m.6311902
241 times.
It's not best option if other user snip/delete some part of the quote in some cases. I think check post history works better.