Interesting that you recall the exact time that the hockey game ended, but not the music playing while you proposed; we'll give you the benefit of the doubt and assume you were too overcome with emotion (nerves?) to hear. And you don't say whether she accepted or not and whether this information is important to you for the celebration of your future anniversaries, or if you just want to ensure you don't ever inadvertently hear it again. Again, we'll assume the former.
We contacted the fountain people at Bellagio, who were most helpful. As we addressed in a previous QoD, the fountain show is currently choreographed to 29 different pieces of music on a revolving schedule, although sometimes this is subject to change if high winds mean a less dramatic show needs to be performed, for example. However, on the night in question, the fountain manager is fairly confident that the schedule went as follows (we have adjusted the times to reflect MST):
The 8 pm show featured "Con Te Partiro" ("Time to Say Goodbye") performed by Sarah Brightman and Andrea Bocelli. The 8:15 pm show was performed to the accompaniment of "Gayaneh - Suite: Dawn, Ayeshe's Dance" from the ballet Gayaneh, performed by the London Symphony Orchestra. And the final show that hour was at 8:30 pm and featured "Viva Las Vegas," which we figure you might have noticed.
So the show director would bet on the fact that you popped the question during the 8 pm show -- it's a very romantic piece and they get a lot of calls about it. Hope this helps!