forget Bobby he's done, after popping his cherry he left a little DNA calling card when the vic tore his shirt.....then he goes and drops his piece! Even the SQ should be able to figure that one out quickly.
Well that is standard practice for (Hollywood) mob hits.
They use a 'clean' gun not implicated in a prior crime and with no traces back to the killer, they use someone with no direct connections to the victim, etc.
For police to match DNA, they need a suspect DNA to compare against.
I don't know that we've ever seen any reason for Bobby's DNA to be in a Canadian data bank. His trip was probably under some assumed identity.
Obviously if someone gets nabbed for some petty crime and starts to squeal, connections could eventually be drawn back to Bobby.
But that's a stretch, and remember Sopranos is about the characters and stories, not about solving crimes using fantasy science. The way the episode opened is more in keeping with how convictions seem to happen on the Sopranos... some 2 bit character screws up or sings when they get pinched, or some inconsequential event leads to something bigger.
That is one of the main plot vehicles of the Sopranos.... Chris and Paulie murder a waiter over a tip, Vito ends up clipping a guy arising from a fender bender, etc.