question re changed buy orders

Can anyone help explain:

Yesterday I placed a 300K buy order on BRO at $0.008

After I placed my order I looked at the depth and it was approx 1.3million on the buy at $0.008... so I figured that there were 1 million in front of me in the queue.

For the rest of the day BRO traded above $0.008... untill the closing auction, when I looked at the closing trades, and over 2 million had gone through after the bell at $0.008.

Great i thought... my order was filled

However, it appears that my order was NOT filled at all! How could this be?
If someone ahead of me in the queue changed their order from a 1million buy to a 2 million buy at $0.008... does their original place in the queue get preserved, or do they join the back of the queue with the ammended order?

Cheers,

MisterMoon