iflynething,
First off, don't be afraid to admit when you've screwed up. I think you will find that you'll get more respect from your fellow pilots by being honest. No one likes to admit that they were at fault, but trust me, you'll come out looking like a bigger man when you do. As far as putting two packs on a Y, it will work, but not if you forget to charge them.
If you have an extra channel open on your receiver you can just plug the second pack into that, no Y connector needed. You also
won't need a diode. One pack will not drain into the other enough to notice on one flight. You should always check both packs before each flight with a good Expanded Scale Voltmeter. A second pack is also gonna add 4 to 6 ounces of extra weight to the plane. All of this is usually overkill for a .40-.60 size plane, so a better alternative for longer flight time would be a single pack with a bigger mAh capacity. If your existing pack is a NiCAD, you can switch to a NiMH pack with about twice the capacity and still weigh about the same.