Warren's full speech is available at archive.org:
"Unfortunately, however, many of our people and some of our authorities and, I am afraid, many of our people in other parts of the country are of the opinion that because we have had no sabotage and no fifth column activities in this State since the beginning of the war, that means that none have been planned for us. But I take the view that that is the most ominous sign in our whole situation. It convinces me more than perhaps any other factor that the sabotage that we are to get, the fifth column activities that we are to get, are timed just like Pearl Harbor was timed and just like the invasion of France, and of Denmark, and of Norway, and all those other countries."
Hon. Earl Warren, pg 11011-11012, San Francisco Hearings, February 21 and 23, 1942, part 29, National Defense Migration
First of all, crushes can get to the state where it is really hard to think rationally about them (Love and Limerence by Dorthy Tennov includes several example of irrationality). So I recommend trying to think rationally, but always consider the possibility that you are completely or partially wrong.
Second, realize that your own estimate of their attraction to you may very well be in the statistical noise range. From
"Benefit or burden? Attraction in cross-sex friendship" by Bleske-Rechek et al. your estimates of their attraction is much more correlated with how much you are attracted to them then they are attracted to you.
reports of attraction to each other were weakly, but not significantly, correlated, r(87) 1⁄4
.19, p 1⁄4 .09. However, men’s attraction to their female friend was strongly associated
with their estimate of how attracted their friend was to them, r(87) 1⁄4 .61, p < .001, and
women’s attraction to their male friend was strongly associated with their estimate of
how attracted their friend was to them, r(87) 1⁄4 .49, p < .001."
Third, remember Conservation of Expected Evidence. For anything that you consider a signal, consider if you would consider the opposite happening to be an opposite signal.
Fourth, I expect that if you were rational about it, you would end up with something like P(they have a crush on me) = .2 or something like that. Eventually, if you want to increase your certainty, you have to actually do something where their response actually gives you good evidence. Unfortunately, these do have the chance of rejection. But I recommend leaving a way out when you do this. I have had good friendships result from romantic rejection.
Lastly, be a friend to them. Most long term romantic relationships are also friendships. It is a lot more fun to think about what interesting thing you want to tell them, or waiting to see what they bring up in conversation, than obsessing over a few glances.