It needed to be in the contract. It would be (or not be) on a form that looks similar to this. If you did not include something like this in your offer for the property, then your offer did not specify what personal property was included. While the washer and dryer were advertised as part of the sale, that is just the advertisement. You negotiated terms that were different than what was advertised.
You have to write that in the actual contract so both parties sign acknowledging that. We always do that when they mention something "will be done" in the MLS description.
I don't know how Maryland works, but here in Washington your agent should have checked the washer and dryer box if you wanted it included. If it's not checked then the listing agent and sellers can assume you don't want it.
It needed to be in the contract. It would be (or not be) on a form that looks similar to this. If you did not include something like this in your offer for the property, then your offer did not specify what personal property was included. While the washer and dryer were advertised as part of the sale, that is just the advertisement. You negotiated terms that were different than what was advertised.
I live in Maryland and I'm going to echo what was said above because the same thing happened to me (not with a washer and dryer, though) and I took Contract Law as part of my business degree in college (graduated from the second biggest college in Maryland). The listing is an advertisement. It is not a binding contract. The binding contract occurs when the sale happens.
@Everett Baker, I agree with everyone's comments, technically it needs be reflect that way in the contract. However, you can always make the request that the washer/dryer be included since it was shown that way in the listing and see how the seller/agent respond. Worst case they say no, and you're back to where you are now. Other option is you could offer a couple hundred bucks to purchase the washer/dryer separately if you really want them.