A Blonde Buys A Thermos. Two Days Later, She's Back In The...

Joke: A blonde buys a thermos. Two days later, she's back in the store and wants a refund. The sales person asks her why she's returning it. She replies, "Well, when I bought it, you said it would keep hot things hot and cold things cold, but yesterday I took some coffee and ice-cream to work for after lunch, and all that came out was a luke-warm slush!"