From your question, it seems you were still on probation, as per the Qatari Law the employer can terminate your employment during probation without having to give any notice or reason for termination.

The questions would be, did you have your Residnce Permit Stamped on your passport? Did your employer cancel your RP? Did you have a signed contract? Does yor employer have published HR policies and Procedure, What do they say? Have you had permission to go on leave? Is it documented? Did you collect your financial entitlements as per your contract? ... etc

What type of communication did you have?

You may always consult a lwayer if you would like to sue them