I forgot to cover this in our agreement. The closest thing we had agreed on was I'd put in $20k to buy the existing app and to 'catch up' my investment to just

I forgot to cover this in our agreement. The closest thing we had agreed on was I'd put in $20k to buy the existing app and to 'catch up' my investment to justify me owning 30% as a co-founder. Since he doesn't want me a co-founder anymore, it doesn't make much sense for me to spend $20k to own 30%. Assuming there is no contract, is my understanding reasonable that he should unwind my contributions?