I read this as "It did me well to disappear" or "It was good for me to disappear"/"Disappearing was good for me". I'm definitely reading this syntactically and grammatically kind of as if it were Spanish, so I don't know if those work in Romanian... anybody know?
Maybe you are mixing the gerund (dispărând) and the gerundive (dispărare). I think they are the same in Spanish – desapariciendo, could that be? – and in English – disappearing – but not in Romanian: dispărând = who disappears, dispărare = the (process of) disappearing. And by the way – can't you say el desaparecer in Spanish?
Edit: See RotariuAna1's correction below. Thanks.
It does not exist such a word in Romanian language: disparare. It is 'dispariție' the process of dissapearing.
What you are saying would have been "Mi-am făcut bine dispărând".
(El) mi-a făcut bine. = He did me good
(Eu) mi-am făcut bine = I did me good