I have been living in a house in Southern California for 18 months and while crawling around under the far end of the house I found that there is about 2 inch deep lint over a 200 sq ft area where my gas clothes dryer vents into this crawl space. I would like to find a way to put in a lint trap rather than change the whole layout of the garage.
To answer OP's question;
There could be a hole in the exhaust pipe that is allowing the lint etc. to leak out before reaching the exit end of the pipe. Repairing that with a tape appropriate for the conduit may solve your problem.
If the pipe simply terminates once it's in your crawl space, and you can access the exit end of the pipe, a length of Nylon Stockings closed at 1 end and a clamp appropriate for the pipe would solve the issue, noting you will have to remove this collector periodically to remove the collected lint.
I don't like the "OMG" abbreviation and seldom use it, but in this case OMG! It would have been bad enough to vent an electric dryer into a crawl (lint, moisture, fire danger), but to vent a gas dryer into a crawl is unconscionable. Gas dryers vent carbon monoxide. It interferes with your body's ability to transport oxygen. If that seeps into the house it could create a myriad of problems, not the least of which is killing the occupants.
Get that thing vented properly, regardless of the cost. Risking your lives on this failed setup isn't worth it. And clean out the lint, it's a fire hazard.
As George Anderson's answer says, this is extremely unsafe and must be fixed. But don't try to fix it by making expensive modifications to your home. Gas and electric dryers are inefficient anyway, and it would make a lot of sense to replace the gas dryer with a heat pump dryer (which doesn't need a vent).
Heat pump dryers operate like a dehumidifier, using the heated dry air on one side to evaporate moisture from the load, and circulating the air to the cold-side coil to re-condense the moisture and expell it as liquid water, recycling the (very high!) energy content to re-heat the dried air and pass it back through the load.
In a comment since moved to chat, @stannius posted a useful link. While many heat pump dryers are small apartment-size units with low capacity, according to this article, "both Whirlpool and LG make full-size heat pump dryers". Some following further links and search suggested the price might be $1500-1800 - considerably more than a cheap gas or electric dryer - but the cost is likely to be a lot less than having the necessary modifications made to your home professionally, including properly fixing everything torn up in the process, especially if you can sell the old unit and recover some of its value.