This argument is more of a philosophical argument than a scientific one. It reminds me of the classic "if a tree falls in the woods and no one is there to hear it, then does it make a sound?". The purpose of this statement is to question whether the observer is a requirement for something to be real.

Ultimately, I think science doesn't have a solid answer to this question. Quantum mechanics might suggest the answer to be "no", since matter exists as a probability function until something measures (observes) it. This would suggest that a lack of observer would leave matter in an exotic state which would not allow such a definite process as falling in the woods. On the other hand, general relativity would suggest that the tree would make a sound because all matter affects the spacetime continuum whether an observer is there or not. This would suggest that the tree's existence is independent of an observer.

Of course, the big issue in science right now is that we have failed to disprove both quantum mechanics and general relativity; but these two primary theories of science are incompatible with eachother. Ultimately, this means that this question regarding physicalism is presently unanswerable by science.