Your best choice would have been to try and organize the group behind -- it was really a bridge too far. If you couldn't get there in a short high speed effort, there is no way you could have gotten there by pacing yourself. There's a reason that the group was ahead of the peloton and shelled your team mate -- they were going faster or just as fast as the field. You had it pegged at around ~48kmh, which is reasonable for a bridge if it was windy. Any slower and there's no way you could close on them in a flat race. The only time a "pacing" approach works for a bridge is if you have other riders bridging, the front group isn't working well, you're an excellent time trialist, or if the course isn't super flat or easy.