My 3.5 year old DD broke the soap dish off the wall above one of our sinks. I'd like to repair it in a way that is durable, easy, and at least moderately aesthetically pleasing. I'm not worried about it looking "like new" though, as nothing in our 1964 house does. Whoever buys it from us (likely in a year or two) will probably gut the bathrooms and kitchens, and this won't be the only piece of repaired tile work when the time comes to sell.
What should I use as an adhesive? I've done some Googling, but I mostly found stuff about when the whole panel falls off the wall (typically) in a shower. I just want to "glue" the broken piece back on. Should I use grout? Thinset? I realize that this is not the ideal solution, but I'm not interested in trying to get the whole tile off (and potentially end up with a bigger project) since we're likely going to sell (and sell to someone who is going to remodel) in the not too distant future.
Thanks!