phantom leak that fixed itself? I recently replaced my front tire. About 3 days post replacement I noticed that the pressure in that tire was at about 50psi (Its a road bike - I keep it around 120).
I pumped it up and hoped for the best for my ride home.

I didn't have time to check for the leak that day so I left until the next day. 
Next day the pressure was fine. 

about 5 days later it again dropped down to around 50 and I pumped it up. 

Now its been about 2 weeks and the pressure is holding as well as it usually does.

Whats going on here?
Luck, most likely. 

You probably have a slow leak, which you could treat by replacing the tube or just keep pumping air in as necessary. Less plausibly, theres something up with your valve. You could try taking the tube out of the tire and pumping it up with a bit of air and putting it in your bath tub to see if you can find some bubbles. 

[In the comments, DRH has the reverse ordering on plausibilities]