Even with 'mild' weather, the boxes (on the trucks) can get HOT when it's not cold out.
I've added the insulated box, and cold packs, whenever I've ordered from either MidWest, Northern Brewer or Rebel Brewer. IF I'm getting my yeast locally, then I'll even get a cold pack if it's not 50F (or lower) out.
Contact MidWest and tell them what happened with the yeast you got from them.
Personally, IF I ever get a packet of Wyeast that doesn't swell within a few hours (at least to some level) I'll be taking it back. Since I make starters a few days (or more) ahead, it's no issue. I can push the brew day off until the following weekend if I must due to that.
BTW, pitching closer to the starting yeast cell count is never a bad thing, or unnecessary. Just as properly oxygenating your wort is not a bad idea. I've been making dual stage/step starters lately, so I can get my pitch cell count with two small starters, compared with needing one LARGE starter if a single step. A stirplate makes it even easier. These are simple facts/truths. If you select to not go that route it won't make you a lesser brewer. But, you'll be denying your yeast additional resources/opportunities to do great things for you. IMO, getting even better brew makes these few, easy, items well worth the expense (mostly dollars, since it's minimal time).
:fro: