Yes it was, Isdaniel.
The fact that God forbids dealing with the mediums suggests there is more to it than the fact they do not exist.
In 2 Cor 12:2. St Paul writes that 'he knew a man' who was caught up in a third heaven and heard 'inexpressible' things that man is not allowed to utter. Could this be an early account of a NDE? Scholars wonder whether this man was St Paul himself.
There are things that we are not allowed to delve into but it doesn't mean they do not exist.
No, the dead are dead. It was not Samuel, it was a lying spirit...
2Ch 18:19 And the LORD said, Who shall entice Ahab king of Israel, that he may go up and fall at Ramothgilead? And one spake saying after this manner, and another saying after that manner.
2Ch 18:20 Then there came out a spirit, and stood before the LORD, and said, I will entice him. And the LORD said unto him, Wherewith?
2Ch 18:21 And he said, I will go out, and be a lying spirit in the mouth of all his prophets. And the LORD said, Thou shalt entice him, and thou shalt also prevail: go out, and do even so.
Ahab wasn't the only one who had a visit from a lying spirit.
As far as Paul goes, it was a vision.