Having a few bad days

Sidney started regurgitating this week out of the blue. I'm pretty sure it wasn't something he ate off of the ground (I didn't see anything when I was cleaning up after him). I know that it happens from time to time, but I made sure to keep a really close eye on him to make sure he didn't show signs of aspiration pneumonia. He hasn't RG'd for a day or so now - so we might be through it. Poor little guy.