On the table are two rules Silver Lining & You also need a Baked Potato. So if someone gets the goal but doesn’t have the potato can she win, because Silver Lining says that Creepers don’t prevent you from winning. Since the Potato is a creeper and not having it is preventing you from winning, you win?

…or is needing something (in this case the Potato) different from having something (other Creepers) which is preventing you from winning?

A: It’s that second thing you said. The Silver Lining rule means that the presence of a Creeper in front of you does not prevent you from winning, i.e. their presence is completely neutral, instead of negative.

If You Also Need A Baked Potato is in play, then you also need a baked potato – no ifs ands or buts. It does not keep the Creepers absence from preventing your win. It only prevents the presence of a Creeper in front of you from preventing your win.