So sorry for your loss, but welcome to the forum.
Please feel free to post a tribute to your piggy on the Rainbow Pigs thread.
Is your surviving piggy male or female and how old is he/she?
Guinea pigs are social animals and need companions of their own kind.
They do grieve the loss of a cagemate but will get on with business of living so a cagemate is important to them.
There are many factors to consider, so this is my experience which might help.
My girl Merab lost her husboar when she was about 3 years old.
She was very quiet afterwards. I had already started looking for companions for her and decided on 2 baby girls. That way if they didn’t bond the new piggies would still have each other and at least they would live in the same room.
I couldn’t find a rescue near me so resorted to a pet shop about 20 miles away ( more reputable than any closer).
I was fortunate in that Merab bonded almost instantly and now 2.5 years later they still live happily together.
There are others on the forum who have lots more experience and wisdom to offer but hope this helps.
Don’t forget you are grieving too so be gentle and kind with yourself.