It is a relatively common occurence. The wake can exist quite a considerable distance behind the aircraft that is creating it. You can compare it to passing through the wake of another boat or ship. Where it is a large vessel, you don't want to get too close or the turbulence can be quite uncomfortable.
With jet aircraft moving at around 8.5 miles a minute, two aircraft crosing each others path at right angles might do so with only a seperation gap of 30 seconds or so. It is quite likely in those circumstances to encounter a couple of bumps (tram tracks) as you cross over the wake. Normally it is quite a light transistion, but sometimes as you discovered it can be more noticable.