Hi.. He is learning to deal with a loss. As a 5 year old that toy has an emotional value like a relationship has for a young adult. Try to help him deal with that loss without holding grudges or any other negative feelings. Try to help him realize that finding something and loosing something is a part of life and that life always have more to offer than it takes away. Try not to preach him rather help him understand together with you gradually.
And No, don't worry, this pain is temporary and it is not going to have any deeper impact on his mind. But yes, series of such learnings and the way we cope with them as a child, does shapes our mind in a certain way. So try helping him learn a positive approach to deal with such set backs in life.
Next Steps
Consult a Psychologist.
Parent/Child Counselling is required.
Health Tips
Mr. Gunjan Maithil
Senior Psychologist
Cell: nine six seven one three zero three one three four
Website: https://gunjanmaithil.wixsite.com/therapy
App: http://wix.to/fECHB08?ref=cl