I do not know the definitive answer. There has been talk, in the past, about whether failure of an IVA actually severs the trust created by the arrangement. I have an inkling that it might not unless specifically dealt with at the time.
I have read,again, in the past, that some firms do sever this trust, so there must, I assume, be some mechanism for it. One firm in particular uses R3 terms and conditions, which may well vary on this point to Protocol Terms.
Were I in this position I would argue that the subsequent bankruptcy subsumed any trust or claim created by the IVA .... but ..... it could have created it's own. However, assumptions again - I assume the BR ended successfully and would therefore assume that the trust, as in a successfukl IVA, only captured those matters that existed during the arrangement (as with PPI and the like) and that, as long as the windfall came into being after discharge, it is yours.
However, all this bluff and bluster are merely my barrack-room thoughts and I would suggest, if it might become an issue, a brief consultation with a solicitor versed in insolvency law.
Final thoughts ... if you did get a windfall .... who would know ? Tick the 'no publicity' box ( do they still have those ? ).
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014