Technically you are out of status since your date of layoff. I am not sure why you would resign, without putting up another H-1B application in place first. Anyways, whatever the motivation, you are entitled to the salary for the work you have already performed. As to the notice requirement, there is non specified under immigration law. Your contract of employment and local rules are controlling in that matter. Proceed through an attorney, to ensure your status is protected and you get your withheld salary.
You need to talk with an attorney that handles labor claims. In most circumstances your employer is not allowed to "send" you "to client place" if it is a different location than listed on the H-1B petition. And your employer cannot refuse to give you your last paycheck.