Understanding Form 16 and Form 16A
If you are a salaried employee, you should ask for Form 16. If your income is other than salary, like a consultant, you should ask for Form 16A.
Filing Returns for FY 2012-2013
You seem to be filing your returns for FY 2012-2013, for which the last date will be 31-07-2013. It's the duty of your employer to issue you Form 16/16A before the stipulated month (much before your last date to file returns). If you don't receive your form, raise the issue with the concerned Income Tax Officer.
Filing ITR for Salaried and Non-Salaried Individuals
If you are a salaried employee, you need to file ITR 1, where you have to fill in the TDS deducted details and nothing more. For this, you might need Form 26AS. If you are non-salaried and filing your return as a professional, you file ITR 4, where you need Form 16A, which has a certificate number mentioned. This number needs to be mentioned in your return, whereas Form 16 doesn't have any certificate number.
So, I guess you can just fill the TDS details in your return even if you don't have Form 16 based on your Form 26AS.
Cheers!