apparently no one thought to talk to Tobe to find out the truth of Emily, her father, and Homer Barron.

Yes, the whole Tobe situation is anybody’s guess. We know he is old, black and completely loyal to Miss. Emily. He is first described as, "an old man-servant – a combined gardener and cook". So, he did pretty much everything for this old lady including tipping off the town that she might be dead. I'm not sure why nobody talks to Tobe but I can speculate that he was not the talking sort of guy. He seems as private as his employer. If we examine the dates Tobe could very well have been a product of the Civil war era. Perhaps he liked the isolation and employment afforded to him by Miss. Emily. In any case he just walks out after her death. He probably did have many secrets about that old lady but we can only speculate to why he kept them to himself. If he was so loyal to her in life it would make sense he would be loyal to her in death. That's my best guess and I'm sticking with it!