The reflections are likely going to be opposite in sign from the indicent signal. One option is to use the findsignal function in the negated version of the signal. I doubt there is any robust way to find all of them and their phase relationships to the original signal, however the functions listed in the documentation section on Signal Modeling may provide some options.
Also search the File Exchange. This search on signal reflection (and your own searches) could discover appropriate functions.
I have never done anything like what you want to do, so these are simply my exploration of the documentation and the File Exchange looking for possible solutions.
