yep; there is nothing that prevents an IO to ask you to send the old passport.
However, you can be ready to provide the required documentation and provide this information upfront - did you raise a police compliant when you had lost (I bet you would have; else you would not have got the new passport); do you have any other documentation that helps accompanying the situation?
have all the docs handy, and send them along with the explanation... this should not be a big issue - CHC is NOT issuing passports, and is just stamping passports. So, if your country has already issued a new passport with all the due diligence handled, CHC would not have much of an issue!!
This is my view; you may wait for others to respond!
all the best!
