12lb line is not bad but heavier won't hurt. I like 15 to 17 mono for topwater type fishing. On most spinnerbaits, buzzbaits and topwater lures, unless there small lures, heavier line won't affect action. Mono tends to float so it won't pull your bait down.
As far as the bass missing your bait. I would have thrown right back but burned it across were it was and then killed (pause the lure) it from time to time