I would say that if in a pinch, store in plastic, but only in a pinch. Any container made of plastic is simply a less good option. Plastics tend to leech into what's inside of them. Which means your scooby could become host to chemical components of that same plastic. This process is sped up by heat, so when talking about a scooby I'm sure it's not being heated. Nonetheless, plastics do leech and I don't know that we've done enough testing on this process to varify that it doesn't happen in when the plastic is kept cool.

From my view, storing it in plastic in a cool, semi-dormant state, due to lack of oxygen, although not ideal from a health standpoint, it is far removed from a warmed, actively brewing culture.

Essentially, we're talkin best practices and mindfulness here, not absolutes.

For example, at the moment you're reading this it's very likely you're wearing clothing, siting on furniture or touching at least a dozen different kinds of plastic. The inhaled out-gassing from the hot plastic casing of your computer likely has far worse outcomes than those from two weeks of your culture stored in a plastic container. But you gotta make a reasonably conscious decision in there somewhere, no?