Hi! Thank you for your question.
General information about termination of a sublease agreement
This is a sublease agreement; your landlord is the sublet and you are the subleasee. A termination of such an agreement has to be done according to the law. The sublet can terminate the agreement three months prior to the date the sublet wants the subleasee to leave. The time of notice, three months, will start the upcoming month. For example, if you sublet terminate your agreement 22nd of July, your time of notice will start the 1st of October. This is a compulsory rule, meaning your sublet cannot put this aside. The parties can however mutually agree on a one month notice if the subleasee wants to, but the sublet is still bound to the three-month notice. Your agreement is specified to a certain time, such an agreement should expire and the end date, but if the lease has been going on for more than nine months, the lease should always be ended by a termination of the contract. Both parties are bound to the specified time, meaning that the sublet cannot end the agreement whenever he or she wants to.
How should the termination of the contract be done?
According to the law, 12:8 hyreslagen, the termination should be done in writing if the sublease agreement has been going on for more than three months. The termination has to be served to the subleasee. The fact that the sublet does not state a reason for the termination does not make it invalid. This rule applies both if the termination is done prior to the end date or on the end date of the lease. The sublet must however include the date he or she wants to end the agreement on.
If it is a normal lease, the termination should be done by registered mail. However, when it comes to a sublease, the court has ruled that a termination could be legal by e-mail, given that the receiver confirms the e-mail. If a termination done on Facebook is legal is hard to answer since the court has not ruled on this issue. Since a Facebook is quite similar to e-mail it might be legal, this is however just a guess.
What can you do?
I recommend you to contact Hyresgästföreningen (The Swedish Union of Tenants). Hyresgästföreningen can help you with questions regarding your lease, especially in situations like these when your sublet has terminated your agreement. Follow this link to get their contact information.
To sum it up, since your agreement is specified in time, your sublet cannot terminate it whenever he or she wants to. You are also entitled to a three-month notice and your sublet has to state the dates on the termination of the contract. Weather the termination on Facebook is legal is not crystal clear, I therefore advice you to get in touch with Hyresgästföreningen who can help you.
I hope this answer helped you in some way.