The usual terms for paying through Rapipago and MercadoPago are that the buyer and seller have to confirm that the deal went through to their mutual satisfaction.
For example, I sell computer equipment and will receive a purchase for a motherboard worth say $1000 with the buyer opting to pay with one of the two options i just mentioned and the notification email from Mercadolibre will show a credit of $1000, but it's not yet available to me.
Once I've posted it off, the buyer receives it and scores me POSITIVE, the $$ then become available to me. It has to be like this to combat fraud.
That should be the situation with you right now. Do you have his telephone number? How's your Spanish?
There is actually a member here who works at Mercadolibre but I can't remember his name.
If you're in any doubt at all, PM either me or anyone else you think could help.
Edit: the member who works at ML is wongjuh and has also posted on this thread.