Dear Angelwngs,
First of all, I'm so sorry to hear about the loss of your little Elvis.
Secondly, I can say with absolute certainty that his physical death was not your fault. It would take longer than just a few hours for an animal to die from lack of water; and not cleaning his cage for a day or two would not result in his death either. Perhaps he had an underlying illness that you were not aware of -- because Guinea Pigs are animals of prey, they are adapt at hiding illnesses and weaknesses. Or perhaps it was just his 'time' to go.
I'm also sorry that you could not give him the burial you wanted to. But Elvis does not hold this against you, because his body is just a vessel that is of no importance to him now. He is in a wonderful place full of joy and happiness; where he is surrounded by all his favourite treats. And, remember a part of him will always be with you, in your heart and in your memories.
Please, don't blame yourself.
Take care of yourself and please come back to let us know how you're getting on. We would also love to see a picture of your little Elvis if you feel up to sharing one

Cheryl x