You can use
dpkg --search /lib/modules/<kernel version directory> to find what packages this directory (and inside) belong to, then use
apt-get --reinstall install <list from before> to reinstall any affected package missing, thus restoring missing content.
In one liner this should be (remove the
-d once sure of the effect):
apt-get -d --reinstall install $(dpkg -S /lib/modules/4.14.98+ | tr ',:' '\n\n' | head -n -1)
As I don't know well if RPi follows the usual kernel installation method (
depmod etc.) you should then check that after this you can modprobe any random module (eg: the
dummy module) not already loaded before considering everything is fine.
PS: in case of additional dkms modules, above won't track it, but you can then continue the "restoration" with
dkms status to get a list and
dkms install module/module-version -k 4.14.98+ to put back what's missing etc.