I am so sorry that you had to go through all of that time and for nothing.  Generally speaking, mediation is non-binding unless the parties agree or the law permits.  Arbitration is what is binding.  So even though your husband agreed to the give you the house he is not now bound by that agreement.   Please read the mediation agreement.  See what it says about being binding.  And ask your attorney if the law allows you to bring it up at all in the divorce trial - but I highly doubt it.  It can not be evidence of anything except a huge waste of your time and money.  Good luck at trial.