Your exit from the company was close on the heels of closure of the company. In that case, you could have little cautious and approached this forum within a month on your exit. Now the company is closed and issue of the backdated experience letter is not legally tenable.
Anyway, did you speak to MD of the company? What he says? If he is avoiding taking the calls, then approach the Labour Officer under whose jurisdiction your company fell into and explain your problem. Do not disclose to him that the company is closed now. Just give him MD's name and number.
Please note that Labour Officer is government appointed authority and he is different from labour lawyer. Latter is professional who works in individual capacity.
From India, Bangalore
Keep a copy of your last bank transaction from the company. Your appointment and this bank document is sufficient to prove your employment. If you are being specifically asked for the document; convey them that the company was closed and you could not collect it.
From India, Chennai