Iron Golem dispawn after I went a little far from the Golem iron

So I made a slime farm in my world, and to lure the slime to magma block I used an iron Golem, and it worked. After that I afk a few hours, well after afk, .I left the slime farm, when I wanted to go again there were some lost Golem iron. This incident has happened twice and the second time, it also disappeared even though it was given a name tag