For the WAVE applications built on safety beacons, it is imperative that the neighboring vehicle information be collected as quickly and efficiently as possible. But the unreliability of broadcast transmission and the randomness of channel access in the IEEE 802.11p MAC hamper the collection process. Specifically, the process suffers from essentially a form of the classic Coupon Collector's Problem, where it takes longer and longer to obtain the remaining information. In this paper, we solve the problem by introducing the application-level acknowledgement of the safety beacons. We demonstrate that this optimization drastically reduces the collection completion time, eventually contributing to the safety and efficiency in WAVE-based systems.