Look, I know life happens. The batteries are dead, or the dog ate the probe (it happens). If you’re flying blind, look for visual cues.
The meatloaf should be pulling away from the sides of the pan slightly. The juices should run clear, not pink. And the top should have a nice, caramelized crust that makes you want to whisper sweet nothings to it.
How Long To Cook A 2 Lb Meatloaf At 375 : Italian Style Meat Loaf
Another trick: stick a butter knife into the center. Hold it there for 10 seconds. If the blade comes out hot to the touch, you’re in a good spot. If it’s lukewarm, it needs more time.