At the reception, Ted and Robin begin discussing a big announcement, and when Barney overhears, he harasses them until they relent, telling him of what happened 2–3 weeks before the wedding.
The proposal was actually meant for a couple at another table; when the mix-up was clarified, the other woman accepted, but Robin's horror and subsequent relief unearthed unresolved issues between Ted and her.
The restaurant owner forced Ted to return the blue French horn in order to get his credit card and driver's license back.
Barney is again disgusted by this idea, not on the terms of their relationship, but due to concerns of his being lonely in New York and Argentina being economically unstable.
Ted and Robin then reveal that after they had sex that night, they realized that their relationship was not heading in a direction either of them wanted to follow, and that they could no longer pretend that these issues did not matter to them.
Through a flashback to the episode "Showdown", they explain that they decided to hold off announcing the breakup because of Lily and Marshall's impending wedding.