Write to the Head of HR to that firm, requesting for a relieving document on the humanitarian grounds. Offer them to pay for the rest of the remaining Notice Period.
They may consider your request, if only you can really influence them to. State the conditions in which you left the firm and share how it was impossible for you continue.
Hope this helps ! Do let us know, once you get the letter from them. Wish you all the best !
I doubt if you can get experience certificate, as you did not get relieved by following prescribed formalities. If you don't mind, You absented from the post without getting your resignation approved and relieved formally by the company. Getting job abroad cannot be termed as personal emergency, but self interest. On termination on misconduct being absent unauthorisedly, you lost all the rights to get other formalities completed by the company. In other words, you severed all the relations with your employer at your own without observing proper formalities.