Not that this definition of simulation matches what most people think when this question gets asked.
The answer is no you can't tell no matter how hard you try. Quantum behaviors should be enough proof that our reality can act way outside our sense of things at very small scales. Any kind of "eureka!" claims about our universe being a simulation can more easily be explained as it just being how our universe works and of course it doesn't line up with human common-sense notions of causality/physics/etc.
And not that it is even an interesting question but my take is no this is not a simulation. Way too much detail. Even if some civilization had the resources to run a simulation the size of our universe it would be a massive waste to do so. The most efficient computational system for simulating a universe with the high fidelity our universe has is to create a universe and let it evolve.