In many cases, a better indication is the cashing of your filing fee checks. For this reason, you might want to consider checking with your company's accounts payable people. In particular, the government might cash the checks before sending you the receipt.
You may be encouraged to know that some employers are still having those checks cashed. Yesterday, for example (April 27) one current F-1 student called to say that it happened with him and his employer. I was happy to hear this news, because I still had not received his receipt. I expect to get it in the next few days. In other words, the government can cash the filing fee checks before sending you the receipt.
Therefore, even if you haven't heard anything by now, you still could have been selected. It isn't over until your employer receives back your petition papers, along with the uncashed checks.
The above information does not constitute legal advice and does not form an attorney-client relationship.
Calvin Sun, Attorney at Law
610-296-3947, cell 215-983-3723
We chat: calvin_t_sun