First of all, state law dictates how a company has to pay you, so you can go to www.dol.gov, find a link for wage and hour and then look for a link to the different state laws. There is a page that shows what each state law is for getting paid.
For hourly positions if a company pay's bi-weekly - many pay a week in arrears, meaning you have to work a full two weeks to get paid for one.
More than likely that is the case here, which means you probably should have gotten paid for two days (for Thurs/Fri) on this check. However, it also depends on when the payroll cut-off dates are. Someone SHOULD have explained this all to you when you were hired.
You really need to check with your HR/payroll department and ask the following:
1) Was I supposed to get paid on this check? (they may have genuinely made a mistake in your new hire processing and won't realize it until you tell them!)
2) If not, when will I get paid? How many days will be on that check?
3) Do you pay a week in arrears?
4) What is the payroll cut-off date?
5) Do you have a payroll calendar? (So that you can see when the payroll cut-ff dates are, when payroll has to be submitted by, and when pay dates are)