Why would modinfo say a module is not found when it appears with lsmod

I have noticed several cases where, if I use lsmod to find a module and then use modinfo for that module, it comes out with a ERROR: Module not found message. For example with the Nvidia module (When using the proprietary drivers).

So in what cases would a module appear on lsmod but give an ERROR like the one I mentioned above with modinfo.

It's being aliased. In my example (similar to yours perhaps):

lsmod | grep nvidia
nvidia               9171294  51

modinfo nvidia
ERROR: modinfo: could not find module nvidia

modprobe --resolve-alias nvidia
nvidia_current

grep -r nvidia /etc/modprobe.d/
/etc/modprobe.d/nvidia-graphics-drivers.conf:alias nvidia nvidia_current

modinfo nvidia_current
filename:       /lib/modules/3.7.5-030705-generic/updates/dkms/nvidia_current.ko
alias:          char-major-195-*
version:        313.09
[...]

Above should speak for itself, doesn't it?