Shavua Tov. There is an interesting ירושלמי that claims that איוב, Job, was among the Egyptians who suffered during the Plagues.
However, he was included among those described as “הירא את דבר ה׳”, those that feared Hashem. This was during the plague of ברד, hail. Those who feared Hashem during the plague of hail removed their animals so that they would not be harmed.
In the Book of Job, he is referred to as ירא את ה׳, which was a similar use of words. Thus, they connected Job with hail.
This also explains how there were horses that remained that were connected to the chariots that chased after the Jewish people when they left Egypt.
There are many details connected with the Plagues and the exodus. Somehow the sages found explanations to all that transpired.