Firstly you have to establish what the deed actually was. If it was a deed of declaration of trust declaring that all though you are both named on the title to the property you own all the equity on it then it in best practice it would have been registered although this is not a necessity for it to be enforceable.
The deed could have been a Land Registry transfer deed actually transferring the his ownership to you but I doubt this because the mortgage lender's consent would have been required for this and you would have to have demonstrated sufficient income in your sole name to take it on yourself (I note you say it is still in joint names).
The position is that a restriction can be entered against a property that is in joint names in the event of one owner's bankruptcy or personal debt but the other owner's interest in the property is safe so if the property is sold pursuant to a Court Order then you will receive your proportional share of the equity according to your percentage interest.
The Courts have wide powers to set aside transactions that were done for the purpose of defrauding creditors - ie. siphoning off assets - and it is possible that they may claim this in respect of the deed drawn up. It remains to be seen if they will or not, you will have to speak to the trustee in bankruptcy about this and dispute it stating that you were in effect a creditor of his at the time of the deed.
In summary, you've got to get a copy of the deed (write to him or the solicitors if you do not have one) and produce this to the trustee to demonstrate your interest. You must then be pro-active in engaging with the trustee to see that you are kept up to date as to whether they apply for an order for sale or seek to disclaim the deed you executed.
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