This is nothing as dire as the loss of a parent but young children really get affected by even small changes etc in ways that it is hard to realise.
My DD had some decorating done to change around two bedrooms for the forthcoming new baby. They went to stay at Mils around the corner for a week as all the furniture ended up in the main bedroom and it was not safe for a toddler. DGS is very familiar with her house but kept wanting to go back home.
He moved into his new room but was unsettled at nights.
Then Sil went to USA with work for a week and one morning DGS had thrown all his toys and books about his room which was very unsual for him.
DD & DGS then came to us for two nights. He was very excited about the idea, but in the end it proved a bit too much and he would have been better staying at home. On the last day I was playing with Dgs and he seemed to get very angry and upset and throwing his toys about. I tried talking to him and he started crying. He is normally a very happy little chap. I am sure now all the changes had just been too much in one go.
I caught up with DD yesterday who said he has been good, but he has been very clingy to his Daddy since he returned. He was told Daddy was in America and could repeat that, but that concept is way to much for a 2.5 yr old to fully comprehend, they do not have the sense of time needed to cope with too much disruption.
I remember something similar with DD after we went on holiday when she was 10 months. She was unsettled when we were away but as soon as we were home she sat in her high chair looking around the kitchen and giggling happily. I am sure she was just very relieved to be back somewhere familiar.