PeptideSynthNJ said:

The distinction that matters is unopened versus in use.

Cold chain shipping for storage and cold: my last order arrived with the cold pack completely melted and the vial at room temperature. I contacted the vendor and they reshipped with better insulation.

What to look for in shipping: temperature monitoring strip inside package. If your peptide arrives warm, contact the vendor immediately. Don't assume it's still good.

Following on from anders_CPH — and this may be the naive question:

What would you measure differently if you were starting again?

BethLabQueen said:

Cold chain shipping for storage and cold: my last order arrived with the cold pack completely melted and the vial at room temperature.

There is a second half to this that has not been said yet. If two explanations both fit, the useful question is which one predicts something the other does not. That is answerable; arguing about which sounds more plausible is not.

Closing the loop on my own question.

Update: the excursion was survivable and the vial was fine. I now keep a cheap fridge thermometer, which costs nothing and ends the argument.

Dr.BariatricHTX said:

If two explanations both fit, the useful question is which one predicts something the other does not.

Agreed, and the size of the effect matters as much as its existence. Something real and small gets treated here as though it were real and decisive.