If we believe the spirit of a man is in his soul of the man, then you could say the spirit was in the soul of the OT prophets. But the Holy Spirit was ‘upon’ the spirit not IN the spirit, not even with Moses. Until the Cross the Holy Spirit has not been in a man, except maybe Melchizadek because he had an eternal status as a priest forever.
But if we simply believe what the Spirit of God says, then rather than making a distinction the Holy Spirit did not make, the point is that the Holy Spirit was in men such as the OT prophets:
Searching what, or what manner of time the Spirit of Christ which was in them did signify, when it testified beforehand the sufferings of Christ, and the glory that should follow. (1 Peter 1:11)
For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost. (2 Peter 1:21)