My first issue is this: If you didn't have 8 hours available, why did you even show up? As Ovah stated, it's ultimately OUR responsibility to keep track of our hours. Yes, the company does (and many times they are off, I found out) but the DOT says it's YOUR job to do so. Do you keep a running tab of your daily hours? What if you get pulled in a scale or over by a portable and asked to recount your hours? Can you? Oh, you say you're on electronic log book? What diff does that make? YOU are still required to keep track of your hours.
Bottom line is: If you don't have hours available, tell them the day before or that day. Don't wait for them to tell YOU.
Another is this: If you didn't have hours available, you must have already been on OT, right? You've already got your 40 hour guarantee for the week, right? If so, you get no more guarantees.
Another is this: Who cares what the package car kids are doing? Do you REALLY want to come in and load/unload/sweep floors/sort, etc.? If they company lets them do it and they don't scream about their hours, so be it. They don't have to send in daily logs to the DOT like feeder drivers.
Another thing that was addressed here: The DOT has long established (but most often been ignored by the company AND shifters OR CPU drivers and rarely challenged) that anytime you are behind the wheel of a DOT regulated vehicle, whether it be a shifter, rail tractor, or even stuck in traffic for hours at a time, that time is reported as "On-duty-driving". You are still bound by DOT regs that mean you can't DRIVE more that your daily allowance, you can't WORK more than your daily allowance, you can't go OVER your daily or weekly allowance, except in special circumstances, like one 14 with the required time off afterwards.
Many other conditions would apply but that's it in a nutshell.