Anthony activates [Mishra's Workshop](http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=383015) to add {3} to his mana pool. He casts [Bronze Sable](https://gatherer.wizards.com/Pages/Card/Details.aspx?name=Bronze%20Sable), leaving him with {1} in his mana pool. This mana comes with a restriction that it may only be used to cast artifacts.

Next, Anthony activates [Xenagos, the Reveler](https://gatherer.wizards.com/Pages/Card/Details.aspx?name=Xenagos%2C%20the%20Reveler) to add {G}{G} to his mana pool. He casts [Elsewhere Flask](https://gatherer.wizards.com/Pages/Card/Details.aspx?name=Elsewhere%20Flask). This leaves him with one mana in his pool. Elsewhere Flash resolves, and Anthony draws a card.

We arrive at an ambiguous game state. Anthony failed to specify exactly which mana in his pool he was using to cast Elsewhere Flask. Does he have {1} in his pool with a restriction, or {G} in his pool with no restriction? Does the game back up to before it became ambiguous? Does Anthony get to choose? Are any penalties awarded?

Assume that this scenario occurred at Regular AND Competitive REL. Describe the outcome of both if they happen to be different.