I dont understand why people get themselves into these situations. If in a rental property, the LL is responsible for the fixtures and fittings that are there. If the bed was not in an acceptable condition, you should have brought this to the landlords attention the following morning and demanded a usable bed.
You are now in the scenario whereby the house came with a bed and it is probably on the contents list of your rental agreement. If you hand back the house with no bed then the LL is perfectly entitled to demand a replacement bed, irrespective of the state of the old one, as you now have no proof of its condition.