All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
You should know that the statement of Al-Qurtubi that reads, "... nobody from human beings is able to see them …" refers to the angels and not the Prophets because the pronoun refers to the closest noun (antecedent), i.e. the angels in this case. In fact, a group of Companions and allies of Allaah (Awliyaa') have been soundly reported to have seen the angels, according to well-known Ahaadeeth.
As for seeing the Prophet, sallallaahu ‘alayhi wa sallam, while awake, it is a mere claim that is not supported by evidence. On the other hand, if you mean by 'experiencing the spiritual form of the Prophet, sallallaahu ‘alayhi wa sallam’, feeling his presence as urging the person to honor and revere him, then there is nothing wrong with this.
An example of this is when the person feels that the Prophet, sallallaahu ‘alayhi wa sallam, is addressing him personally when reading the Ahaadeeth - the commands and prohibitions. Another example of this is when the person invokes blessings and peace upon the Prophet, sallallaahu ‘alayhi wa sallam, in the Tashahhud. The worshipper uses the Arabic pronoun “Kaaf,” i.e. the second person pronoun in the Tashahhud. The usage of the second person pronoun “Kaaf” (="you") in the word "‘alayKA" (="upon you") indicates the strong feeling of the presence of the Prophet, sallallaahu ‘alayhi wa sallam, as if the worshipper is addressing him directly.
Ibn ‘Uthaymeen said, “Are the Words, "As-Salaamu ‘alayka" (i.e. "peace be upon you") addressed to the Prophet, sallallaahu ‘alayhi wa sallam, as people address one another? The answer is, no. If that were the case, the prayer would be invalid, because the prayer should not contain inter-human discourse. If that were the case, the Companions (during the lifetime of the Prophet ) would have spoken these words out loud so that the Prophet, sallallaahu ‘alayhi wa sallam, could hear them, and he, sallallaahu ‘alayhi wa sallam, would have returned the greeting to them as they used to do when they met him. Shaykhul-Islam Ibn Taymiyyah said in his book Iqtidhaa' As-Siraat Al-Mustaqeem: “You address him in such a way because it is as if he is present in front of you given your strong mental attachment to him during the prayer.”
Allaah Knows best.