@Jessica2562 Are you positive that the listing didn't mention a pet fee? It would be stated in the House Rules section, not necessarily the description.
I don't understand the part about the message from Airbnb saying you didn't have to message the host before booking. A person who travels with 3 dogs, or has any other circumstance a host should know about should always message a host before proceeding to book, in order to ensure it will work for you and the host.
If a host doesn't answer your message, that's a bit of a red flag, and normally you shouldn't book there, but if you expect to book somethlng last minute and show up right away, not giving a host time to answer (expecting an answer within minutes is unreasonable- not everyone is free to answer a message immediately, people have jobs, families to attend to, may be driving, etc. Airbnbs aren't hotels with 24 hr. reeception.), this sort of thing is likely to happen to you again.