Runners have short lifespans. They tend to croak on the job. So you'd be denying it to the person investigating the circumstances around said runner's death, which would vary depending on where said runner died. May be a Corporate Court investigation crew, could be Interpol, could be Knight Errant/Lone Star. At the end of the day all that matters is that it draws questions back to where the tech originated. 50,000¥ for a CEO's "Night on the Town" is a lot easier to explain than an unmarketed, never reported stolen, SOTA piece of equipment in a runner's hands. As for traceable, things as pricey and rare as Delta are going to be traceable to a good degree. You're talking about needing expensive and rare custom tailored parts integrated perfectly and installed by some of the most skilled surgeons in an area. Likely just looking at the composition of the parts would narrow down the field tremendously without going into other details.
Now, Corps may not report the theft, but that will cause issues with Insurance policies, and always looks shady. Ripe grounds for more digging. Stolen and blackmarket equipment is a big market, which leaves to how it gets into the market place. For SOTA and prototypes, it's either going to be additional tech that was pulled other than the job, or its going to be tech that the Johnson is trying to rid himself of. Tech disappears from Ares, winds up 6 months later on a dead runner. Makes it easy to look like the runner took it rather than S-K having paid to get it and pawned it off on the runner as payment for an unrelated job.
When you get down to it though, if it's important enough to hire a team of runners to snatch and grab a prototype, or worth enough to pay runners with instead of handing out money, it's probably going to be important enough to chase after.