They are protected quite well, compared to sellers actually, but unfortunately even with all the protection measures fiverr has in place, still issues arise and scams happen, from both sides.
If you agreed on 1 day delivery with the seller and they didn´t only not just not deliver after 1 day, but even after 3 additional days not and are asking for more time you can ask the seller for cancellation (if they accept, your money will be refunded then by fiverr, your seller btw actually doesn´t have your money yet, during the delivery time and the following clearance period the money stays with fiverr), or take it to Customer Support, if the seller declines or if their behaviour was that unacceptable that you don´t want to discuss with them.
Sorry that happened to you, don´t let it spoil fiverr for you, there are loads of honest sellers who do deliver their orders on time. Doesn´t help you in this case of course, but listening to your hunches or clues next time is certainly a good idea, we sellers have to do that often too, and we have much less clues than buyers can get to go on, but of course I know it´s not that easy in all categories, and also of course it´s especially difficult, if you´re pressed on time and need something done within 24 hours.
Hope you´ll get it sorted out with seller or Customer Support, and that you have better luck finding the right seller for you next time.
Happy holidays to you either way!