Can we find out who sent the takedown notice?
This is the part that matters. Anyone can DMCA anything
However it is supposed to be from the copyright owner [17 USC 512(c)(3)(A)(i)] and if it isn't, it can be ignored [17 USC 512(c)(3)(B)] and makes the person who does it liable for damages [17 USC 512(f)(1)]. Although that's probably pretty hard to use in practice.