My dear sweet person - whoever you are, you are a credit to humanity....your PIGGY was so so lucky to have you as a mummy.
The same thing, very similar, happened to me last January. A darling sweet boy, Reggie died after I submitted him to the somehow barbaric but necessary act of castration...we had handreared him because he had been poorly with his dental problems before, so he was a guinea in a million - and I think most owners know what I mean by that - the special one....the squeaky cuddly one that looks into your eyes.
He died after the operation in January this year and I still shed tears and feel responsible. Others tell me 'He had a lovely life - don't beat yourself up'....easier said than done. I shall always remember Reggie as you will always remember Piggie. One day you will be reunited. I have just lost a little scrap of life tonight and am very emotional...so I empathise with you fully. You are a lovely person and should go on and adopt other guinea pigs - you did your best my love. Piggy knows that.