Forge has a problem. Technically Forge has many problems but today we are going to investigate one of them. "Why does Momentary Blink not work?"
Let me briefly explain how Momentary Blink is supposed to work. (Basically Momentary Blink saves your creature from damage or destruction.)
1. You play Elvish Piper, a puny 1/1 creature
2. Your opponent plays Shock and targets Elvish Piper
3. You play Momentary Blink
4. Shock is countered, aka fizzles, because it does not have a legal target
The problem is that Forge doesn't process Momentary Blink correctly and Shock is perceived to have a valid target thus putting your Elvish Piper in the graveyard. The reason that Forge does this is because it sees both Elvish Piper's as being the same. And you may ask, "Why?"
Forge uses card objects (Java source code) to represent physical, cardboard cards. Card objects are used everywhere that a physical card is used: in hand, in the graveyard, on the battlefield, exiled or in your library. Card objects are equal if they have the same unique number.
The problem is that Forge doesn't assign a new unique card number to Elvish Piper after Momentary Blink resolves. This error can be easily solved by giving each creature (and permanent) a new unique card number when it enters the battlefield. But the issue of "card uniqueness" continues to be a complicated, thorny problem.
Keep on forging,
--Ideally the user interface wouldn't show each card's unique ID number but I didn't know how to draw fancy pointing arrows like Magic Online.
--I thought this was a great card picture from Magic upcoming set Innistrad and I wanted to show it off.