you've probably already figured this out, but bloodhounds q is a cone in front of you, not 360 degrees around you, its very likely that the enemy just wasn't in the cone since it would be really narrow closer to you and you said he was not very far from where you used it.

How far can bloodhounds scan?

The maximum distance it will highlight is 75 meters. It will also tell you how many hostiles were detected. With the maxed number of detected hostiles being 10, any higher will read as "10+ HOSTILES DETECTED". Enemies caught in the scan will see 'SONAR DETECTED' on their HUD.

Does Bloodhound scan all around?

“This is the game we play competitively, Bloodhound scan directly on a full team, nobody shows on scan,” tweeted NRG's Chris 'sweetdreams' Sexton.