So this song isn't in the credits and nobody seems to know it, but I have to try here, nonetheless, since I really loved it.
So the song appears around minute 13:00, just after Robin asks Ted "Risk it?" and Ted replies "Risk it", then the scene goes to where barney notices Ted drinking beer and Robin water, resulting in him thinking that Robin may be pregnant. In this whole scene I just described features a song with no vocals, which starts after the "Risk it" and ends before the "No" Barney says after noticing the drinks.
I have been searching for it for more than 3 years and no luck! If someone here happens to know the song please tell me the name of it, drives me crazy not to know! Thanks!