Client claiming I did not spend the night on an overnight stay?

I have an awkward situation I'd like to ask your opinion on. I have sat for this client several times in the past with no issue and lots of praise. Today is the day after the house sitting ended and the client is saying they believe I did not stay overnight with their dog. I absolutely stayed there every night of the stay and throughout most of the day except for a few trips to the store during the day. The client's reasoning is that the bed looked unslept in and the alarm company records show that the garage door was opened the same time as the alarm was set.

I told the client I stayed there every night of the stay and would never not stay at a home overnight. I also explained in summertime I don't sleep with any blankets even with AC because I have hot flashes (embarrassing to have to explain to a client) That I cleaned the areas I used thoroughly before I left and straightened up the bed. I also let them know that I exit to the guest house through the garage doors (not the big one but the ones that lead into the garage then out back to the guest house) I have another sitting job with them in about a week and so far no response after I sent them my explanation. Have any of you experienced this? If so how did you handle it especially if it is a regular client?

Thanks for any advice you guys can offer. I'm just so upset that this is happening especially with a client I thought I had a great relationship with.