Sent pen-pal some goodies, never heard back

My pen-pal and I like to exchange little trinkets with eachother.

One time she sent me two envelopes of goodies in a span of a few weeks.

I thanked her through e-mail and when I had time, sent her a package back.

I didn't feel obligated to send her something back, I didn't want to out-do her, I WANTED to send these things to her just because and I'd never expect anything in return other than a reply. The value of the goodies wasn't much at all (just stickers, paper, pens, some postcards from my country...)

but since I haven't heard back from her (while usually she replies really fast), I feel like perhaps I put her in an awkward position (maybe she thinks the value was a lot?).

I want to send her an e-mail today to see how she's doing, but I'm wondering, should I mention that she shouldn't feel obligated to send me anything since I'm already happy with just an e-mail, or should I just ignore that part and pretend like I never sent her anything?

Have you considered the possibility of your package having got lost along the way? Postal services are not infallible, unfortunately, and I've had it happen to me; I wouldn't have known about it if I hadn't asked my penpal if she'd received my package.

You can say something like "Oh, by the way, I sent you something last week/month/whatever, I wonder if it's already reached you?", and then reiterate she doesn't have to send you anything in return.

Thanks for your reply.
Actually, that didn't cross my mind at all! Thanks for reminding me. I guess I'll just ask whether the package has arrived :)