Irregular behavior observed on Kraken

This post is not meant as an accusation against Kraken (which I hold in high regard), but rather as a effort to understand the behavior I observed two days ago.

I had placed a limit buy order for Ripple at 0.00007619 BTC/XRP, and shortly after the order was placed, the price of Ripple dipped below the limit order, to 0.00007613 BTC/XRP. Yet, my buy order remained untouched. Why did this happen? Isn't any sale order supposed to be either partially or fully matched with the highest buy order? I do not know for certain that my buy order was the highest, but it was certainly higher than the price with which the order in question was filled. The dip below my buy order happened about 20 seconds after my order was placed. Could it be that the trading engine upgrade in January makes the users see their orders filled on the client side before they're actually filled on the server side, so as to make it seem like orders are placed quicker than they actually are? That would explain why my order was ignored by the system.

While it doesn't really bother me that I missed out on what would become a 3% price increase, I wish to further understand how the Kraken trading engine works, so if you've experienced something similar or have knowledge to share, make sure to drop a comment.

Cheers!